UNIT-1 Mother Board: Introduction To MotherBoard:
The shape and layout of a motherboard is called the form factor. The form factor affects where individual components go and the shape of the computer's case. There are several specific form factors that most PC motherboards use so that they can all fit in standard cases. The form factor is just one of the many standards that apply to motherboards. Some of the other standards include: The socket for the microprocessor determines what kind of Central Processing Unit (CPU) the motherboard uses. The chipset is part of the motherboard's logic system and is usually made of two parts -- the northbridge and the southbridge. These two "bridges" connect the CPU to other parts of the computer. The Basic Input/Output System (BIOS) chip controls the most basic functions of the computer and performs a self-test every time you turn it on. Some systems feature dual BIOS, which provides a backup in case one fails or in case of error during updating. The real time clock chip is a battery-operated chip that maintains basic settings and the system time. The slots and ports found on a motherboard include: Peripheral Component Interconnect (PCI)- connections for video, sound and video capture cards, as well as network cards Accelerated Graphics Port (AGP) - dedicated port for video cards. Integrated Drive Electronics (IDE) - interfaces for the hard drives Universal Serial Bus or FireWire - external peripherals Memory slots
A motherboard is the heart of a computer. It is the main printed circuit board present in the computers which holds the main electronic components of the system like the central processing unit and memory and also provides the connectors for other important peripherals. A motherboard is a large system in itself which contains a number of subsystems like the processor and other components. The basic function for which a motherboard is used in a computer is that it holds the important electronic components of the system including the memory and central processing unit and helps in establishing some sort of bridged connection between other internal components of the system. Motherboard affects the speed of the computer system. A good motherboard, which will be properly compatible with the components of a computer system, will enhance the speed of the computer, while a motherboard which is not compatible with the components of a computer system will negatively affect the speed of the system. There are different types of motherboard which are available. AT Motherboard An AT motherboard is a motherboard which has dimensions of the order of some hundred millimeters, big enough to be unable to fit in mini desktops. The dimensions of this motherboard make it difficult for the new drives to get installed. The concept of six pin plugs and sockets is used so as to work as the power connectors for this type of motherboards. It is mainly produced in the mid 80’s and this motherboard lasted a good span from the Pentium p5 to the times when Pentium 2 had been started to be used. ATX Motherboard Advanced technology extended, or popularly known as the ATX, are the motherboards which were produced by the Intel in mid 90’s as an improvement from the previously working motherboards such as AT. This type of motherboards differ from their AT counterparts in the way that these motherboards allow the interchangeability of the connected parts. Moreover the dimensions of this motherboard are smaller than the AT motherboards and thus proper place for the drive bays is also allowed. Some good changes were also made to the connector system of the board. The AT motherboards had a keyboard connector and on the back plates extra slots were provided for various add- ons. LPX Motherboard The low profile extension motherboards, better known as LPX motherboards, were created after the AT boards in the 90’s. The major difference between these and previous boards is that the input and output ports in these boards are present at the back of the system. This concept proved to be beneficial and was also adopted by the AT boards in their newer versions. The use of a riser card was also made for the placement of some more slots. But these riser cards also posed a problem that the air flow was not proper. Also, some low quality LPX boards didn’t even have real AGP slot and simply connected to the PCI bus. All these unfavored aspects led to the extinction of this motherboard system and was succeeded by the NLX. NLX motherboard (New Low-Profile EXtended motherboard) A low-profile PC motherboard from Intel for slimline cases, introduced in 1987. Unlike boards for desktop and tower cases that hold the expansion cards perpendicular to the board, cards plug into a riser card on the NLX and are parallel with the board. BTX Motherboard BTX stands for Balanced Technology extended. BTX was developed to reduce or avoid some of the issues that came up while using latest technologies. Newer technologies often demand more power and they also release more heat when implemented on motherboards in accordance with the circa-1996 ATX specification. The ATX standard and the BTX standard, both were proposed by Intel. The first company to use, or to be precise, implement BTX was Gateway Inc, followed by Dell and MPC. Apple’s MacPro uses only some of the elements of the BTX design system but it is not BTX compliant. This type of motherboard has some improvements over previous technologies: Low-profile – With the larger demand for ever-smaller systems, a redesigned backplane that shaves inches off the height requirements is a benefit to system integrators and enterprises which use rack mounts or blade servers. Thermal design – The BTX design provides a straighter path of airflow with lesser difficulties, which results in better overall cooling capabilities. Instead of a dedicated cooling fan, a large 12 cm case-fan is mounted, that draws its air directly from outside the computer and then cools the CPU through an air duct. Another feature of BTX is the vertical mounting of the motherboard on the left-hand side. This kind of feature results in the graphics card heat sink or fan facing upwards, rather than in the direction of the adjacent expansion card. Structural design – The BTX standard specifies distinct locations for hardware mounting points and hence reduces latency between key components. It also reduces the physical strain imposed on the motherboard by heat sinks, capacitors and other components which are dealing with electrical and thermal regulation.
Pico BTX Motherboard Pico BTX is a motherboard form factor that is meant to manufacture even smaller size BTX standard. This is smaller than many current “micro” sized motherboards; hence the name “Pico” has been used. These motherboards share a common top half with the other sizes in the BTX line, but they support only one or two expansion slots, designed for half-height or riser-card applications. Mini ITX Motherboard Mini-ITX is a 17 × 17 cm (6.7 × 6.7 in) low-power motherboard form factor. It was designed by VIA Technologies in year 2001. These are largely used in small form factor (SFF) computer systems. Mini-ITX boards can also be cooled easily because of their low power consumption architecture. The four mounting holes in a Mini-ITX board line up with the four holes in ATX specification motherboards, and the locations of the back plate and expansion slot are the same. Although, one of the holes used was optional in earlier versions of the ATX. Hence, Mini-ITX boards can be used in places which are designed for ATX, micro-ATX and other ATX variants if required. Motherboard Basics A computer has many components, each with their own roles and functions. The role of the motherboard is to allow all these components to communicate with each other. Considering the fact that all the other components are installed on the motherboard or connected to it, it is safe to say that the motherboard is the central piece of a PC, the component that brings it all together. Processor Socket The processor socket is the central piece of a motherboard, usually being located near the center of the motherboard. It’s also the central piece because it holds the processor – the brain of your computer. Power Connectors No computer component can operate without power, and a motherboard is no exception. The power connector, commonly a 20 or 24-pin connector, can be situated either near the right edge of the motherboard, or somewhere close to the processor socket on older motherboards. This is where the power supply’s main connector gets attached, providing power to the motherboard and all the other components. Newer motherboards have an additional 4-pin or 8-pin connector near the processor, used to supply additional power directly to the processor. Memory Slots Located in the upper-right part of the motherboard, the memory slots are used to house the computer’s memory modules. The number of slots can vary, depending on motherboard, from 2, in low-end motherboards, all the way up to 8 memory slots, on high-end and gaming motherboards. It is important to pay close attention to the type of memory a motherboard supports, in order to buy the appropriate memory modules. Newer motherboards support DDR3 memory, the current industry standard memory architecture, but motherboards with DDR2 memory slots and even DDR1 memory slots are still present on the market. An interesting aspect is that there are some older motherboard models that supported different types of memory, and usually come with two DDR1 memory slots and 2 DDR2 memory slots, or two DDR2 slots and two DDR3 slots. These motherboards were great options for people that wanted to upgrade a motherboard without having to upgrade all the other components as well. The number of memory slots should be an important criterion to take into account when choosing a motherboard, as it will determine the maximum amount of memory you can install.
Video Card Slot This is the type of slot that doesn’t need an explanation, as its name doesn’t leave much room for interpretation as to what its role is. Coming in the form of a PCI-Express slot on newer motherboards or AGP on older ones, the video card slot is situated right below the processor. It is not uncommon for older motherboards, especially those that target the office segment, to lack this slot, meaning that you won’t be able to install a discrete video card, thus having to rely on the integrated one. At the opposite pole, high-end gaming motherboards come with multiple video card slots, allowing the installation of multiple video cards in a SLI or CrossFire configuration. Expansion Slots Expansions have the role of letting you install additional components to enhance or expand the functionality of your PC. You can install a TV tuner, a video capture card, a better soundcard, etc. – you get the idea. These ports are located under the video card slot, and come in the form of PCI slots (on older motherboards) or a scaled-down version of PCI-Express slots (on newer motherboards). Some motherboards come with both types of expansion slots. The number of slots is usually dependent on the format of the motherboard – larger motherboards (full ATX) have more, while smaller formats (micro- ATX) have fewer, if any. IDE and SATA Ports IDE and SATA ports are used to provide connectivity for the storage devices and optical drives. The IDE interface is somewhat outdated, so you shouldn’t be surprised if you see a lot of new motherboards coming without this type of port. It was replaced by the smaller and much faster SATA interface, which currently reached its 3rdrevision, being able to achieve maximum speeds of up to 600 MB/s, as opposed to the IDE interface, which can reach a maximum of 133 MB/s. It is not uncommon for manufacturers to include SATA ports of different revisions, such as two SATA2 ports and two SATA3 ports. Considering the fact that most optical drives on the market come with a SATA connector, and these devices are not bandwidth-hungry, using a SATA2 port for an optical drive is perfectly acceptable. In fact, most mechanical hard drives cannot achieve SATA3 speeds due to mechanical limitations, so unless you plan to use multiple high-performance solid state drives in your PC, which can benefit of the higher speeds of SATA3, a combination of SATA2 and SATA3 shouldn’t make much of a difference.
BIOS Chip and Battery The BIOS chip contains the basic code needed to take your computer through the boot process, up to the point where the operating system takes over. Since the BIOS code is stored on a memory chip that needs constant power to function, a battery is also present to keep the chip powered when the computer is unplugged. Northbridge and Southbridge If you have a look at your motherboard, chances are you’ll see a square metal component somewhere in the lower-right part of the board. This metal component is actually a heat sink, and its role is to provide thermal protection for the Northbridge – one of the most important components of a motherboard. The Northbridge is responsible for coordinating the data flow between the memory, the video card and the processor. A secondary chip, known as Southbridge, has a similar function, coordinating the data flow between the processor and peripherals such as sound cards or network cards.
Front Panel Connectors, USB Headers and Audio Header The front panel connector is where all the elements present on the front of your case are connected. Power button, reset button, power led, audio connectors and USB connectors – they are all connected to the front panel or the corresponding headers. Rear Connectors These connectors are the bridge between the outside of your computer and the inside. The name is a bit misleading, as the connectors are actually located on the left edge of the motherboard; however, since these connectors are accessible from the outside, the name simply implies where they are accessible from – the rear of the PC case. External peripherals such as keyboard, mouse, monitor, speakers and so on are all connected via these connectors.
Classification as per Approach:
Single-board computer
A single-board computer (SBC) is a complete computer built on a single circuit board, with microprocessor(s), memory, input/output (I/O) and other features required of a functional computer. Single-board computers were made as demonstration or development systems, for educational systems, or for use as embedded computer controllers. Many types of home computers or portable computers integrate all their functions onto a single printed circuit board.
Unlike a desktop personal computer, single board computers often do not rely on expansion slots for peripheral functions or expansion. Single board computers have been built using a wide range of microprocessors. Simple designs, such as those built by computer hobbyists, often use static RAM and low-cost 8- or 16-bit processors. Other types, such as blade servers, would perform similar to a server computer, only in a more compact format.
Single board computers were made possible by increasing density of integrated circuits. A single-board configuration reduces a system's overall cost, by reducing the number of circuit boards required, and by eliminating connectors and bus driver circuits that would otherwise be used. By putting all the functions on one board, a smaller overall system can be obtained, for example, as in notebook computers. Backplane
A backplane is similar to a personal computer's motherboard and sometimes a term improperly used to describe the computer's motherboard. The backplane is a printed circuit board containing connections (slots) for expansion boards and allows for communication between all connected boards.
An example of a backplane used with earlier computers was the NLX form factor, which had connections for expansion cards and a motherboard. Another place you may find a backplane is in a corporate network router, which is a large router that allows the use of expansion boards and modules for enhanced communication.
There are two types of backplane systems; an active backplane and passive backplane. With an active backplane the backplane contains the slots as well as the necessary circuitry to manage and control all the communication between the slots. However, a passive backplane has only the bus connectors and very little or no additional circuitry. In a passive backplane system all the communication is handled by one or more expansion boards that have been connected to the backplane.
Block Diagram Of Mother Board:
A Computer Motherboard is commonly known as Main board or MB or System board or logic board is designed on PCB (Printed Circuit Board).That holds or connects all components and parts together on a single sheet. The Computer Motherboard holds all the circuitry to connect the various components of a computer system. Therefore it is also called as backbone of Personal computer system.
The Main board or Motherboard is the main, cruical and important part of the computer system. It holds many important components such as Computer memory slots,cpu,sata IDE slots, expansions slots(PCI,AGP etc),capacitor’s, resistor’s ,BIOS chip etc The Computer main board is made up of thin sheet of non conductive material from plastic .The traces which are present on the motherboard is made up of copper/aluminum foil.
Components and Parts Used in Computer Motherboard
There are various component embedded in MB/PCB(Printed Circuit Board).You should know the basic computer functionality and uses of the various component attached to main board to use it and installed in Computer case.
Today Computer Motherboards comes in number of variety but the basic functionality and uses are pretty much the same? You must be familiar with the use and aware of the basic architecture of PC and Laptop motherboard design
As it is difficult to understand each and every part of MB still you should be aware of some common and important component & parts attached to it.
List of component of PC Motherboard
Expansion slots (PCI Express, PCI, and AGP) 3-pin case fan connectors Back panel connectors Heat sink 4-Pin (P4) power connector CPU Socket Screw hole Memory slot Floppy connection ATA (IDE) disk drive primary connection 24-pin ATX power Supply connector Serial ATA connections Coin cell battery (CMOS backup battery) System panel connectors Serial port connector USB headers Jumpers SPDIF Game port and MIDI header Internal speaker Keyboard controller Parallel port header PS/2 header
PC Motherboard Component and Their Features
Ps/2 Mouse Connector Circular In Shape 2 Mouse Port 6 Pins Female Type of Connector
Usually Green In colou
Ps/2 Keyboard Connector Circular In Shape PS2 Keyboard Port 6 Pins Female Type Of Connector
Usually Voilet In Colour
Serial / Normal Mouse Connector Serial Port D-Shape Connector 9 Pins Male Type Connector
Display /VGA Port D -Type Of Connector 15 Pins Display Port Female Type Of Connector Usually Blue In Colour
USB Stands For Universal Serial Bus You can Connect any USB Devices to this connecot USB Port Ex: Pendrive,Scanner,Printer,Cardreader Motherboard may contain more than 2 Usb Slot
Used to Acces Internet Lan Port RJ45 Patch cable Is connected Used for Networking
There Are 3 Slots mainly in Sound port 1st Is Light Blue (Input Audio) Sound Port Middle is Light Green ( Output Audio) Last One is Light Pink( Mike)
Parallel Port(Lpt1,Line Printer,Printer Port) Serial-Printer are Connected to this port Printer Port 25 pin Female-type connector D-Shape Connector
• This is cpu socket where processor is Installed. CPU Socket Ram is connected to this Slot Memory Slot (RAM) Slot's are mainly named as (DIMM,SIMM) DIMM stands for(Dual in line memory moudle) SIMM (Single in line memory module)
• SATA (Serial Advanced Technology Attachment)
SATA Post •You can attached Sata (Hard disk ) ,Sata (DvD -Rw) .. Floppy Disk Drive is out of date, nobody uses this device nowadays Floppy Disk Port 34 pin Male Connector
IDE(Integrated Device Electronics) IDE Connector 40 pins connector
There are 3 type of smps power connector (12 Pins,20 Pins ,24 Pins) SMPS-Power Connector SMPS Power Supply is connected here It's gives desired voltages to motherboard converts Ac volt
into Dc
CMOS Battery • Here Cmos battery is Inserted Connector AGP (Advanced Graphic Port) AGP Slot Graphic card is connected in this slot
PCI (Peripheral Component Interconnect) You can connect display card,sound card ,lan card to this PCI Slot slot
• Processor fan is connected here System fan Slot CMOS-Clear Jumper • This jumper is used to clear all Bios setting
Ground +,Ground - DT+ ,DT+ Front USB DT-, DT- VCC+,VCC-
Power Switch Reset Switch Front Panel Hdd Led Power led
• You Can Insert Your Audio Pin In front side of computer case Front Audio to hear sound
Complete Description of Computer Motherboard
The desktop or PC motherboard is mounted inside the computer case with the help of small screws which are used to tighten the system board into the computer case.The computer case possess some pre-drilled holes so that the screws can be easily fit into it.
System or Main board consist of a single CPU socket which is pre-soldered into it. There are various types of CPU socket which are used to determine the computer motherboard and the CPU which is compatible with it.
You can determine which processor is compatible or suited to the motherboard as there is a number printed on the CPU socket which determines which CPU to be installed on it. There are memory slots commonly called as DIMM or SIMM which allow users to install memory (RAM) into it. Number of memory slots depends entirely upon the manufacturer of motherboard.
Expansion slots are used in motherboard so that you can install additional video cards, sound cards, and graphic cards into it. These expansion slots are pre-install. Some of the expansion slots are :: PCI,AGP,ISA etc
Front panel connectors on motherboards has a Power switch, Reset, Power led, HDD led connectors which are connected by wires.
Jumpers are used for specific purposes such as CMOS clear jumper is used to reset bios password.
On the left side of the motherboard, there are number of ports which are used to connect to other peripherals of computer system such as monitors, USB drives, printers, keyboard, mouse,LAN , modem etc
There is a small coin-shaped cell commonly called as CMOS battery which is inserted into a battery connector present in the motherboard.
SATA and IDE slots are available to connect to other devices such as hard drives and DVD- RW with the help of cables. 24 pins power connector is available to connect power supply(SMPS) and additional 4 pin p4 power connector is also available. Installation of Motherboard Mother board is the largest of all boards to be connected in a PC. It lies flat on the bottom of the case. So while mounting Mother Board on the system box one should be careful about size of case and the size of mother board. The smaller motherboard is not a problem but if its size is larger than the size of the case then it may not be mounted. Different methods are used to mount motherboard in its place. The most common method uses a couple of screws and some plastic spacers. Normally the mother board s held down only by two screws but it may use more than two. For mounting the mother board in its place first checks the dimensions of case and board both. If they are compatible then smoothly slide it into its place which is most of the times at bottom of the case. Arrange the holes of mother board on the holes of case and screw them. Once the mother board is fixed into its place you can connect various cables at corresponding connectors. While connecting the mother board you must be very careful. Take following precautions during mounting of the mother board. 1. Do not apply excessive force when tightening the screw because it can wrap the mother board and damage it resulting into failure. 2. There should not be metal brackets and stand offs touching the mother board or its circuitry resulting into a short circuit. Use thin and non conducting washer between each standoff and mother board. Once the mother board is connected in place make other connections and configure properly for the mother boards bus speed clock multiplier, voltage setting etc.
UNIT-2 Buses and Ports:
A bus is a common pathway through which information flows from one computer component to another. This pathway is used for communication purpose and it is established between two or more computer components. We are going to check different computer bus architectures that are found in computers.
Different Types of Computer Buses
Functions of Buses in Computers 1. Data sharing - All types of buses found in a computer transfer data between the computer peripherals connected to it.
The buses transfer or send data either in the serial or parallel method of data transfer. This allows for the exchange of 1, 2, 4 or even 8 bytes of data at a time. (A byte is a group of 8 bits). Buses are classified depending on how many bits they can move at the same time, which means that we have 8-bit, 16-bit, 32-bit or even 64-bit buses.
2. Addressing - A bus has address lines, which match those of the processor. This allows data to be sent to or from specific memory locations.
3. Power - A bus supplies power to various peripherals connected to it.
4. Timing - The bus provides a system clock signal to synchronize the peripherals attached to it with the rest of the system.
The expansion bus facilitates easy connection of more or additional components and devices on a computer such as a TV card or sound card.
Bus Terminologies
Computers have two major types of buses: 1. System bus:- This is the bus that connects the CPU to the main memory on the motherboard. The system bus is also called the front-side bus, memory bus, local bus, or host bus. 2. A number of I/O Buses, (I/O is an acronym for input/output), connecting various peripheral devices to the CPU. These devices connect to the system bus via a ‘bridge’ implemented in the processors' chipset. Other names for the I/O bus include “expansion bus", "external bus” or “host bus”.
Bus Types
These are some of the common expansion bus types that have ever been used in computers:
1. Peripheral Component Interconnect Bus (PCI Bus) : A Peripheral Component Interconnect Bus (PCI bus) connects the CPU and expansion boards such as modem cards, network cards and sound cards. These expansion boards are normally plugged into expansion slots on the motherboard.
The PCI local bus is the general standard for a PC expansion bus, having replaced the Video Electronics Standards Association (VESA) local bus and the Industry Standard Architecture (ISA) bus. PCI has largely been replaced by USB. PCI requirements include: Bus timing Physical size (determined by the wiring and spacing of the circuit board) Electrical features Protocols PCI specifications are standardized by the Peripheral Component Interconnect Special Interest Group.
SCSI(Small Computer System Interface):
Short for small computer system interface, a parallel interface standard used by Apple Macintosh computers, PCs and many UNIX systems for attaching peripheral devices to computers. Nearly all Apple Macintosh computers, excluding only the earliest Macs and the recent iMac, come with a SCSI port for attaching devices such as disk drives and printers. SCSI interfaces provide for data transmission rates (up to 80 megabytes per second).
How is SAS Different from Parallel SCSI? Although SAS and parallel SCSI both use the SCSI command set, how they move data from one place to another is very different. To support point-to-point serial data transport, SAS introduces new types of connectors, cables, connection options, and terminology. Generally speaking, SAS is faster and more flexible than parallel SCSI, and provides more options for building your storage space. SAS lets you mix SAS and SATA disk drives together, and lets you connect many, many more devices.
Difference between Parallel SCSI and Serial Attached SCSI
This table describes many of the main differences between the two interfaces. Parallel SCSI Serial Attached SCSI
Parallel interface Serial interface
Maximum speed 320 MB/sec shared by all Maximum speed 300 MB/sec per phy when in devices on the bus half-duplex mode
Supports SCSI devices only Supports SATA and SAS disk drives simultaneously
Up to 16 devices per SCSI channel More than 100 disk drives per SAS card, using an expander (see SAS Expander Connections) or 50 SATAII disk drives.
Supports single-port devices only Supports single- and dual-port devices
Uses SCSI IDs to differentiate between Uses unique SAS addresses to differentiate devices connected to the same adapter between devices
User intervention required to set SCSI IDs SAS addresses self-configured by SAS devices
Requires bus termination Requires no bus termination
Standard SCSI connectors SAS connectors (see Cables)
Serial Ports: Serial ports are generally built into the mother board, which is why the connectors behind the casing that are connected to the mother board by a wire cable can be used to connect an exterior element. Serial connectors generally have 9 or 25 pins and resemble the following (DB9 and DB25 connectors respectively):
A personal computer generally has between one and four serial ports.
Parallel Ports: Parallel data transmission involves sending data simultaneously on several channels (wires). The parallel ports on personal computers can be used to send 8 bits (one octet) simultaneously via 8 wires:
The first two-way parallel ports allowed for speeds of 2.4Mb/s. Enhanced parallel ports have been developed however to achieve higher speeds — the EPP (Enhanced Parallel Port) achieves speeds of 8 to 16 Mbps, and the ECP (Enhanced Capabilities Port), developed by Hewlett Packard and Microsoft has the same characteristics as the EPP, with a Plug and Play feature, allowing the computer to recognise the connected peripherals.
Parallel ports, like serial ports, are built into the mother board. DB25 connectors allow for connection to an exterior element (e.g. a printer):
What Is a Com1 Port? A COM1 port is a serial port on a computer. A serial port is a socket enabling peripheral devices like a mouse or a modem to connect to the computer via a cable. Serial ports have been replaced by the small Universal Serial Bus Connectors. Newer computers do not have a COM1 port; they connect to peripherals via a USB port instead. LPTI Short for line printer terminal, LPT is used by IBM compatible computers as an identification for the parallel port, such as LPT1, LPT2, or LPT3. The LPT port is commonly required when installing a printer on an IBM compatible computer. The majority of all computers utilize LPT1 and do not have an option for another LPT port unless additional ports are added to the computer. USB Short for universal serial bus, USB (pronounced yoo-es-bee) is a plug and play interface that allows a computer to communicate with peripheral and other devices. USB-connected devices cover a broad range; anything from keyboards and mice, to music players and flash drives. RS-232C RS-232C is a long-established standard ("C" is the current version) that describes the physical interface and protocol for relatively low-speed serial data communication between computers and related devices. It was defined by an industry trade group, the Electronic Industries Association (EIA), originally for teletypewriter devices. RS-232C is the interface that your computer uses to talk to and exchange data with your modem and other serial devices. Somewhere in your PC, typically on a Universal Asynchronous Receiver/Transmitter (UART) chip on your motherboard, the data from your computer is transmitted to an internal or external modem (or other serial device) from its Data Terminal Equipment (DTE) interface. Since data in your computer flows along parallel circuits and serial devices can handle only one bit at a time, the UART chip converts the groups of bits in parallel to a serial stream of bits. As your PC's DTE agent, it also communicates with the modem or other serial device, which, in accordance with the RS-232C standard, has a complementary interface called the Data Communications Equipment (DCE) interface.
Computer Based Instruments Information
Computer-based instruments are part of a computer (a board, for example), or need to be connected to a computer in order to measure and display data.
Types:
There are several types of computer-based instruments. Examples include:
computer-based spectrum analyzers computer-based oscilloscopes computer laboratory instruments
A computer-based oscilloscope transforms a signal into a pattern or waveform and produces a graph of voltage against time on a computer screen. A computer-based spectrum analyzer is an instrument that can also be connected to a computer and is used to measure the frequency spectrum of the signal. A computer laboratory instrument is used for the purpose of analyzing, testing, and verifying various concepts and equipment in laboratories. A technique called digital and vector modulation is popularly used for establishing communication between computers. Other computer-based instruments are commonly available.
Specifications
Computer-based instruments have many specifications and function in a variety of ways. A computer-based oscilloscope has an external analogue to digital converter that can be connected to a PC. A computer-based oscilloscope has several parameters to consider such as:
computer host digital inputs operating temperature maximum shock maximum vibration analog bandwidth number of channels
A computer-based spectrum analyzer displays signal amplitude on the vertical axis and frequency on the horizontal axis. Computer-based spectrum analyzers parameters include form factor, number of input/output channels, and dynamic range. In digital and vector modulation, both the digital and vector modulations are used. In digital modulation, the information to be transmitted is converted into digital form. In vector modulation, a single modulator is used to control both amplitude and phase. Computer-based instruments are designed and manufactured to meet most industry specifications.
Applications /Use Of Computer-based instruments
Computer-based instruments have a wide range of applications in the field of education and research. Computer-based spectrum analyzers can easily measure radio frequency signal intensity, frequency, and also power density through the use of calibrated antennas. A computer based spectrum analyzer can also be used to check whether a wireless transmitter is working in accordance with the federally defined standards. Major advantages of computer-based oscilloscopes are low cost, portable (when used with a laptop), easily handled, and equipped with storage capability. A computer-based instrument can be created to resolve open-ended design problems. Due to the low cost of computers, computer-based instruments are particularly suitable for the educational market where equipment budgets are often low.
UNIT-3 Memory What is the hard disk? A hard disk is the physical medium information storage device of most computerized systems. It is an actual disk that rotates at high speed. The surface is coated with magnetic material, and data is stored magnetically on the surface. A tiny read/write head on the end of an arm that can move over the surface of the disk does the reading and writing to transfer the information to and from the medium. How does a hard disk drive function? A hard disk is a device that is used to store large amounts of data in a computer system. Hard disks differ from other memory because they are non-volatile; they retain the data even when they do not have power. The data, which can be either just informational data, or executable programs, is written onto a spinning disk by making magnetic pulses very near the surface of the disk which make magnetized spots on the disk. The data is comprised of places which either are, or are not magnetized, yielding ones or zeros. The coils which make the magnetic field are on movable structures which "fly" above the disk, in that they are spring loaded to force them toward the spinning disk, but since actual contact would destroy both the coil and the disk, the structure is shaped like an airfoil (airplane wing), so that the relative wind from the spinning disk forces the coil structure just a small distance away from the disk. Hard disk A hard disk is part of a unit -- often called a disk drive, hard drive or hard disk drive -- that stores and provides relatively quick access to large amounts of data on an electromagnetically charged surface or set of surfaces. Today's computers typically come with a hard disk that can contain anywhere from billions to trillions of bytes of storage. A hard disk is actually a set of stacked disks, like phonograph records.
Each disk has data recorded electromagnetically in concentric circles, or tracks, on the disk. A head, similar to a phonograph arm but in a relatively fixed position, writes or reads the information on the tracks. Two heads, one on each side of a disk, read or write the data as the disk spins. Each read or write operation requires that data be located, an operation called a seek. Data already in a disk cache, however, will be located more quickly. A hard disk/drive unit comes with a set rotation speed varying from 4,200 revolutions per minute to 15,000 rpm. Most laptop and desktop PCs use hard disks that fall between 5,400 rpm and 7,200 rpm, while hard disks at higher rpm can be found in high-end workstations and enterprise servers. Disk access time is measured in milliseconds. Although the physical location of data can be identified with cylinder, track and sector locations, these are actually mapped to a logical block address (LBA) that works with the larger address range on hard disks. In 1953, IBM engineers created the first hard disk, which was the size of two refrigerators. The company then shipped the first commercial hard disk-based computer, the 5 MB IBM 305 RAMAC (random access method of accounting and control) in 1956. Parts of a hard drive A hard drive consists of several major components inside its casing. These include the platter for storing data, a spindle for spinning platters, a read/write arm for reading and writing data, an actuator to control the action and movement of the read/write arm and a logic board. Hard disks include one or more aluminum, glass or ceramic platters made of substratematerial with a thin magnetic surface, or media layer, to store data. Platters store and organize data in specific structures -- tracks, sectors and clusters -- on this media layer, which is only a few millionths of an inch thick. A superthin protective and lubricating protective layer above the magnetic media guards against accidental damage and contamination by foreign material, like dust.
The spindle rotates the platters as needed and holds them in position. The rpm of the spindle determine how fast data is written and read. For multiple-platter HDDs, the spindle maintains the platters at a fixed, separated distance to give the read/write arms room to operate. The read/write arm positions the read/write head over the correct places on the disk platter to access or write data. It is the read/write heads that read and write data to and from the platters by transforming their magnetic surface with electric currents. Typically, there is a read/write head floating 3 to 20 millionths of an inch above the top and bottom half of the surface of every platter side. All the read/write arms of a hard disk are fused together in the actuator motor. The actuator motor receives instructions from the HDD circuit board and controls the movement of the read/write arm. It oversees platter data transfers and ensures read/write heads are always in the right place. An intelligent circuit, or logic board, tells the actuator motor what to do. It is located at the bottom base of the unit, called the casing, and a flexible ribbon cable connects the circuit board to the actuator motor that controls the read/write arms. Form factor The entire disk must be mounted in an enclosure to protect the internal environment of the hard disk from outside contaminants and air. The drive's internals, also known as the head assembly, are mounted securely to the casing and then usually covered with aluminum. The form factor of an HDD is the size and shape of this enclosure. The HDD form factor governs its compatibility with the drive bays of desktop and portable computers, servers, storage enclosures, storage arrays or any consumer product that uses a hard disk, such as a digital video recorder (DVR). Industry standards dictate the geometry of HDD form factors, which includes the length, width and height of the HDD, in addition to the orientation and position of the host interface connector. Common enterprise-class HDD form factors are small form factor (2.5-inch) and large form factor (3.5-inch), with the measurements representing approximate diameters of the platter(s) inside the drive enclosures. While enterprise-class HDD enclosures typically have standard lengths and widths, height can vary -- up to 15 mm and 26.1 mm for small and large form factor enclosures, respectively. The 3.5-inch desktop form factor height ranges from 19.9 mm to 26.1 mm, while the mobile 2.5-inch hard disk's height ranges from 5 mm to 15 mm. Hard disk destruction services Just because data is deleted and is no longer accessible to the application or operating system (OS) that created it, that doesn't mean the information isn't available on a hard disk. Formatting a drive doesn't always destroy data bits, neither does overwriting data repeatedly with other data. Specialized programs called hard drive shredders overwrite data and are intended to make that data irretrievable. There are experts who say original data may still be recoverable after using a hard drive shredder, even if the overwriting process used by these programs occurs hundreds of times over. Drilling holes through the hard disk won't necessarily do the trick either, as some tracks will remain unaffected. The only way to ensure that all the data on a hard disk is destroyed is to pulverize the whole assembly. For a fee, companies such as ProShred and Securis will securely pick up and transport a hard disk and shred it much like a wood chipper disposes of brush and tree limbs. They will also certify the data has been destroyed in a manner that meets proper compliance and environmental regulations. Common hard disk errors/faults Hard disks can fail for all sorts of reasons. However, failures generally fall into six broad categories. Electrical failure occurs when, for example, a power voltage surge damages a hard disk's electronic circuitry, causing the read/write head or circuit board to fail. If a hard disk powers on but can't read and write data or boot, it is likely that one or more of its components has suffered an electrical failure. Mechanical failure can be caused by wear and tear, as well as by a hard impact, such as dropping an external hard disk or the computer that houses an internal hard disk. This may cause, among other things, the read/write drive head to hit a rotating platter causing irreversible physical damage. Logical failure results when the hard disk's software is compromised or ceases to run properly. All sorts of data corruption -- such as corrupted files, malware and viruses, the improper closing of an application or shutting down of a computer, human error or accidental deletion of files critical to hard disk functionality -- can lead to a logical failure. The effects of a logical failure vary from recurrent crashes to constant freezing and disk errors, the disappearance of data, inaccessible files and more. Bad sector failure can occur when there is a misalignment of the magnetic media on a hard disk's rotating platter, resulting in a specific area(s) on the platter becoming inaccessible. Bad sectors are commonplace and often limited when they occur. Over time, however, the number of bad sectors can increase, eventually leading to a crash, inaccessible files or the hanging or lagging of the operation of a hard disk. Firmware failure happens when the software that performs the maintenance tasks on a drive and enables the hard disk to communicate with a computer becomes corrupted or stops working properly. This type of failure can lead to the disk freezing during bootup or the computer a hard disk is connected to not recognizing or misidentifying it. Multiple unknown failures that accumulate over time can also occur. For example, an electrical problem could lead to a mechanical failure, such as a read/write head crash. It might also lead to a logical failure, resulting in several bad sectors developing on the hard disk platters. Hard Disk Controller (HDC) A hard disk controller (HDC) is an electrical component within a computer hard disk that enables the processor or CPU to access, read, write, delete and modify data to and from the hard disk. Essentially, an HDC allows the computer or its processor to control the hard disk. A hard disk controller's primary function is to translate the instructions received from the computer into something that can be understood by the hard disk and vice versa. It consists of an expansion board and its related circuitry, which is usually attached directly to the backside of the hard disk. The instructions from a computer flow through the hard disk adapter, into the hard disk interface and then onto the HDC, which sends commands to the hard disk for performing that particular operation. Typically, the type and functions of a hard disk controller depend on the type of interface being used by the computer to access the hard disk. For example, an IDE hard disk controller is used for IDE interface based hard disks.
Floppy Disk Controller (FDC) A floppy disk controller (FDC) is an electronic chip controller used as an interface between a computer and a floppy disk drive. Modern computers have this chip embedded in the motherboard, whereas they were a separate component when they were originally introduced. A floppy disk controller (FDC) is a specially designed chip that controls the reading and writing functionality of a floppy drive. An FDC can support up to four floppy disk drives at a time. The controller is connected to the system bus of the CPU and appears as a set of I/O ports to the computer. It is usually also linked to a serial bus of the direct memory access (DMA) controller. In an x86 computer, the floppy disk controller uses IRQ 6, whereas interrupt schemes are used on other systems. Data transmission is often done by FDC while in DMA mode.
Floppy disk drive Faults Bad floppy diskette Verify the floppy diskette you are attempting to read from is not write protected or bad. Verify the diskette is not write protected by sliding the tab into the opposite position, preventing light from shining through it. If you do not have a tab, place tape over this hole. Not connected properly Verify the floppy connection is connected to the motherboard FDD connector. If it appears to be connected, disconnect and then reconnect the cable to verify the cable is seated properly. Also verify the floppy cable coming from the motherboard is connected to the back of the floppy drive. If connected, disconnect and reconnect the floppy drive cable to verify it is seated properly. Bad drivers If you are not able to read or write to a floppy diskette from Windows, verify the computer is not exhibiting floppy driver issues by testing the floppy drive from MS-DOS. Bad hardware If you are not able to read or write to a floppy diskette after changind the drivers then it means there is a bad hardware problem. Replace the following hardware in the computer in the below order. 1. Replace the floppy data cable that connects the computer floppy drive to the motherboard. 2. Replace the floppy driveif the floppy data cable did not resolve your issues. 3. Replace or request that the motherboard be replaced. Pen Drive A pen drive, or a USB flash drive, is a portable data-storage device. Pen drives have replaced the floppy drives of old and have become the most popular data-storage devices among consumers. Micro, lightweight and handy, a pen drive can be easily carried from place to place by students, professionals, academicians and independent tech consultants. Currently available pen drives with storage capacities ranging from 8GB and 32GB can be used to store graphics-heavy documents, photos, music files and video clips. Transfer Files A pen drive plugged into a USB port can be used as an interfacing device to transfer files, documents and photos to a PC. Similarly, select files can be transferred from a pen drive to any workstation. Portability The lightweight and "micro" characteristics of a pen drive make it possible to carry it from place to place. Backup Storage With most pen drives now having password encryption features, important family information, medical records and photos can be backed up on them.
Ram Module A memory module is another name for a RAM chip. It is often used as a general term used to describe SIMM, DIMM, and SO-DIMM memory. While there are several different types of memory modules available, they all serve the same purpose, which is to store temporary data while the computer is running. Memory modules come in different sizes and have several different pin configurations. For example, the original SIMMs had 30 pins (which are metal contacts that connect to the motherboard). However, newer SIMM chips have 72 pins. DIMMs commonly come in 168-pin configurations, but some DIMMs have as many as 240 pins. SO-DIMMs have a smaller form factor than standard DIMM chips, and come in 72-pin, 144-pin, and 200-pin configurations. While "memory module" is the technical term used to describe computer memory, the terms "RAM," "memory," and "RAM chip" are just as acceptable. But remember, while memory terms may be interchangeable, the memory itself is not. This is because most computers only accept one type of memory. Therefore, if you decide to upgrade you computer's RAM, make sure the memory modules you buy are compatible with your machine.
Common Hard Drive Problems and Solutions
1. Corrupted Files
Corruption of system files usually occurs when the system shuts down suddenly, making it impossible for you to access your hard drive and thus your system. Some of the reasons for the corruption of the system files include power surges, use of malicious program, accidental closure of a running program and improper shutting down of the PC.
The solution to this problem is to make sure that you close down all programs that are running before commencing to shut down your computer. Moreover, when shutting down the computer, you must do so in the standard manner. In addition to this, you should avoid installing malicious programs on your hard drive and keep cleaning it regularly so that no unwanted programs remain there for long.
2. Computer Viruses & Malware
Computer viruses and malware infect the system and corrupt the system files that are stored on the hard drive. These viruses and malicious software usually enter the system from an outside source for instance, the internet and an external hard drive. These viruses first tend to attack the hard disk and then spread to other computers that are linked through the same network.
Keeping your computer’s operating system updated is one of the solutions to this problem. Moreover, another possible solution is installation and frequent updating of an antivirus software program. This antivirus is going to protect your system and your hard drive and make sure that it remains safe from their threat.
3. Manufacturing fault
Hard disks that haven’t been tested beforehand become unresponsive after a few months of use. This problem is encountered usually with new hard disks. The reason for this is more often than not a manufacturing fault which causes the hard disk to fail.
The best way to solve this problem is to be careful when purchasing a new hard disk. It is crucial to test the new hard disk before installing it in your computer system. However, if you have a hard disk with a manufacturing fault and it becomes unresponsive then the only solution available is to replace it.
4. Heat
Heating is a common problem associated with hard disks. If the system is overused, the fans of the hard disk start moving slowly and the system starts heating up immediately after being booted. Moreover, clicking noises can be heard from the hardware of the system too which is an indication that the hard disk is overheated. The reason for this is lack of proper ventilation or a faulty CPU fan which overheats the system to the point that the hard disk crashes.
The solution to the heating issue is to ensure that the CPU fan has been installed properly and is providing sufficient cooling to the hard disk. Moreover, you can install an application that keeps you notified about the temperature of your hard disk. If it starts exceeding the maximum limit, shut down the PC for a while and let it cool down before resuming your work.
5. Computer fails to detect hard disk or BIOS
The inability of the computer to detect the BIOS or the hard disk results from disturbances in the power supply provided by the UPS. This causes the hard disk to not spin properly which causes the PC to not detect either the BIOS or the hard disk.
The best possible way to solve this issue is to ensure that the power supply being used for the hardware components of the PC especially the hard disk are working properly. You can do this by changing the cable connecting the UPS to the hard disk and also by switching to a UPS of a reputable company.
6. Unexpected computer crashes
When the hard disk becomes too old it starts exhibiting all kinds of issues which can lead to unexpected computer crashes. The reason for this mostly is the accumulation of bad sectors over a large period of time. As the bad sectors pile up, the hard disk’s spindle motor malfunctions and read/write head becomes jammed. If this happens, you start hearing grinding noises from the hard disk and files and folders suddenly start disappearing. You can solve this problem by properly maintaining your hard disk and installing anti-virus programs that keep your hard disk clean and protect it from the threat of viruses that can result in the creation of bad sectors. Moreover, replacing the hard disk after 3-4 years is also a good way to avoid this issue.
7. Human Errors:
Mistakes made by the user are also responsible for hard disk failures. For instance, improper installation of operating system, making changes to the settings of the system registry and changing the location of the system files are all human errors that can cause irreversible damage to the hard disk.
Avoid making any unnecessary changes to the system registry settings or altering the locations of the system files. Moreover, make sure that you are installing the operating system properly.
Hard disks are vital for the proper operation of a computer system. However, they are vulnerable to damage and problems which can cause them to lose the data that have been stored on them. However, by taking the necessary precautions, you can avoid the chances of hard disk failure.
Problems with Floppy Disks
With the advent of the rewritable CD (CD-RW) many people are predicting the demise of the venerable floppy disk. Today's computers can even boot from the CD drive. But if your computer is not connected to a network, there is no quicker way to back-up or share a file.
Problems with the floppy drive are rare, but that is not the case with floppy disks themselves. Floppy disks are made super cheap and are very unreliable. Also, floppy disks are sensitive to magnetic fields. If you place a floppy disk on top of your monitor, your computer case, or any metal object, you risk corrupting the disk. If you have a problem reading a floppy disk, it is almost always a bad disk.
Use the following troubleshooting guide:
• Can't read a floppy disk
If you have another system, check to see if the drive in that system is able to read the disk. If the disk works in a different drive, begin by checking for obvious problems. It is not unknown to find an object like a Post-It note or the metal slide protector from a previous disk stuck inside a drive.
• Can't write to a floppy disk
Again, begin by checking for obvious problems. Make sure the floppy disk is not write protected. On a 3.5" disk you should be able to see through the hole in the upper-right corner of the disk (looking at the labeled side of the disk). If there are no files already on the disk, try to re-format it.
• Can't boot from a floppy drive
If your operating system is Windows 2000, or Windows XP Professional, you can't boot from a floppy disk with these systems. Otherwise, make sure the disk you have is a bootable disk. It needs to have been created as a "startup disk" or formatted with the "copy system files" option button selected.
• More complex problems
In order to start faster, today's systems are usually set in the BIOS to boot from the hard disk drive first. Check the boot sequence in the BIOS setup. If the boot sequence starts with the letter of a hard disk drive (like C:), and that drive is having a problem, the system will never even attempt to boot from the floppy disk drive. Go to BIOS setup, and set the boot sequence to start with A.
In some companies, the floppy drives are disabled for security reasons. This is done by either disabling the onboard FDD controller in the BIOS setup, or by removing the power cable or data cable from the drive inside the computer.
• Weird problems
Sometimes when a technician is working inside a computer, they will temporarily remove the data cable from the floppy drive in order to get easier access to another component. They may fail to replace the cable properly, or put the cable on backwards. If the floppy drive's LED is always on, the data cable may be reversed.
Sometimes a floppy disk can be read on the system that it was originally formatted on, but cannot be read on another system and vice versa. This is usually caused by the fact that the head of the floppy drive on one system is out of alignment.
As with all Windows(tm) systems, sometimes the operating system gets confused. If your system can't recognize the floppy drive or can't read any floppy disks, try rebooting the system.
If you are having a problem with a floppy disk, remember they are made super cheap and are not meant to be reliable, but they can still serve a very utilitarian purpose.
UNIT-4 Introduction to Keys
Keyboard has many keys which performs their own functions. Following are the various types of keys found in standard keyboard categorized according to their function or type:
1. Alphanumeric keys : These are the keys which consists of alphabets (a,b,c...... y,z) and numbers (1,2.....0)
2. Punctuation keys : These are the keys which lies in the numeric keys and displays the punctuation symbols when pressed simultaneously with the shift key.
3. Lock keys : Lock keys lock a part of a keyboard depending on the lock setting selected. There are three lock in a keyboard and they are number lock, scrolling lock and capital lock.
4. Direction keys : Direction keys are the arrow keys which helps in moving left, right, up and down.
5. Function keys : Function keys are the soft keys which may have default actions accessible on power-on. these keys lies on the top row of the keyboard. The keys are (F1, F2,...... F12).
Key combination
Here are the details on the use of combination of various types of keyboard:
Alternate (ALT) + Right Arrow will go forward to a page you've previously accessed in your current browser session ALT + Left Arrow will go back to a page you've previously accessed in your current browser session (Remember that the Backspace key will also go back to a page you've previously accessed in your current browser session) Control (CTRL) + F will open a Find dialog to search a page for text. Open Start menu = CTRL+ESC Highlight items in window = CTRL+A Undo = CTRL+Z Holding down CTRL + ALT and pressing the letter C will insert the copyright symbol (©), unless you have already assigned the letter C to a quick launch shortcut, in which case it will launch the associated application. Press the Windows key + the Pause/Break key - Opens up the System Properties dialog. SHIFT+F10: Equivalent of right-click SHIFT+DEL: Deletes immediately without removing to the Recycle Bin SHIFT+TAB: Moves to previous control in the dialog box (TAB alone goes forward, SHIFT+TAB backward) Press Shift when inserting a CD-ROM - Skips auto-run
Here are some additional shortcuts for use with the Windows key (the one with the Windows logo on it):
Windows: Display Start menu. Windows + D: Minimize or restore all Windows (Win98 and later only). Windows + Tab: Cycle through buttons on taskbar; when you release the Windows key, just press the space bar or ENTER key to switch to the window which corresponds to the currently highlighted button. Windows + Ctrl + F: Display find: computer. Windows + F1: Display Help. Windows + break: Display system properties dialog box. Windows key + M - Minimizes all currently running programs on your desktop. Holding down the Windows Start key and depressing the E key - Starts Windows Explorer without having to choose it from the Start | Programs menu. Holding down the CTRL key while depressing either the left or right arrow keys - Cause your cursor to jump from one whole word to another in any word processor. CTRL + C will copy any highlighted text to your Windows Clipboard. CTRL + V will paste any text from your Windows Clipboard to the point where your cursor is currently located. Pressing the Home key will move the cursor or screen display to the very beginning of a line in a Windows document or to the very beginning of a browser page view (in Microsoft Internet Explorer (IE) 5.5 and Netscape 6 only). Pressing the End key- Moves the cursor or screen display to the very end of a line in a Windows document or to the very end of a browser page view (in MSIE 5.5 and Netscape 6 only). CTRL + Home - Moves your cursor or screen display to the very beginning of a Windows document or browser page view (in MSIE 5.5 and Netscape 6 only). CTRL + End - Moves your cursor or screen display to the very end of a Windows document or browser page view (in MSIE 5.5 and Netscape 6 only). Holding down the CTRL + Shift keys while depressing either of your arrow keys will highlight text and/or select graphics in the direction of the arrow key you choose. CTRL + Shift + Home will select all text and/or graphics from the present cursor position to the very beginning of a Windows document. CTRL + Shift + End will selects all text and/or graphics from the present cursor position to the very end of a Windows document. You can also skip files and continue selecting or even go back and unselect files by holding down the CTRL key and clicking your mouse pointer on the additional files or the previous files you decided against selecting. ALT + F4 will close whichever program you are currently using. To close additional programs using this shortcut, click on the program's button on the Windows taskbar then hold down the ALT key and depress the F4 key. The Windows Menu key - Activates a pop-up menu identical to the one activated by your right mouse button. It's a quick way to Undo an action, Cut, Copy, Paste, Delete or Select All on-screen. Holding down the Windows Start key and depressing the F key - Opens the File Search dialog without having to go through two menu levels on the Start | Programs menu. Pressing the F3 key from your Windows desktop will do the same thing. Holding down the ALT key and depressing the TAB key - Displays on-screen currently running programs to which you can switch your screen view. An icon is highlighted when a box encases it. Continue holding the ALT key and press the TAB key repeatedly to cycle through the on-screen icons. When you highlight the icon of the program to which you want to switch, let go of the ALT key, and your PC will switch to that program on-screen. You may also reverse TAB directions by holding down the SHIFT key with the ALT key and pressing the TAB key. To restart the Windows operating system without completely rebooting your computer, follow these steps: 1. On the Start Menu, click Shutdown. 2. Check Restart. 3. As you click Yes/OK, hold down the Shift Key. 4. Continue pressing Shift until you see the words, "Windows is now restarting." This tip does not work with Windows Me, however. To shut down Windows without having to use the Start menu, click your mouse on your Windows taskbar or anywhere on your desktop (except on an icon), hold down the ALT key and press the F4 key. When the shut down confirmation dialog appears, make sure the option you desire is checked, and press ENTER. Here are some remnant keyboard shortcuts from the old days of MS DOS, but they work with Windows as well. 1. SHIFT + DELETE = Cut highlighted text onto Clipboard 2. CTRL+ INSERT = Copy highlighted text onto Clipboard 3. SHIFT + INSERT = Paste contents of Clipboard 4. SHIFT + TAB = Undo tab 5. CTRL + Q + F = Find/Replace text (used to be Find text) 6. CTRL + Q + A = Select all (used to be Find/Replace text) 7. F3 = Repeat last search
The following keyboard function keys perform the same tasks within both Windows Explorer (WinEx) and Internet Explorer (IE), with only a few differences:
o F1 = Starts Help in both o F2 = Renames a file/folder in WinEx; Unassigned in IE o F3 = Activates the Find: All Files feature in both o F4 = Selects a different file/folder in both o F5 = Refreshes the current view in both o F6 = Tabs from pane to pane in WinEx; Highlights the address box in IE o F7 = Unassigned in both o F8 = Unassigned in both o F9 = Unassigned in both o F10 = Highlights the menu bar in both o F11 = Unassigned in WinEx; Sets the screen to Full Screen view in IE o F12 = Unassigned in both
Keyboard Types
83-Key PC/XT Keyboard
The very first PC keyboard was the old 83-key keyboard used by IBM for the very first IBM PCs and PC/XTs in the early 1980s. This design was copied nearly verbatim by most of the early "clone" makers, and was the standard for PCs of this era. In looking at this keyboard one must bear in mind that we are going back almost 20 years, an eternity in the computer industry (which is arguably only about 50 years old period). There are many valid criticisms of the first keyboards, but in fact, IBM made several good decisions for which one must give them credit. For starters, they made a good decision in making the keyboard detachable from the PC at all; we take that for granted, but many small computers of that era, such as the Apple ][, had the keyboard integrated into the system box. A detachable keyboard was a distinct improvement.
Of course, with the first keyboards IBM also engineered the keyboard interface, cabling and signaling standards that are mostly still in use today. In terms of construction these keyboards were very much appreciated by many typists because they were rock solid, with high-quality keyswitches and heavy, metal cases. (Pick up an original IBM keyboard and you'll understand why people say they were "built like a tank".) They are also fairly small and compact dimensionally, taking up relatively little desk space.
From a layout standpoint, however, there are many serious problems with the original 83- key layout, which caused many typists a great deal of frustration. Many of these complaints were based on comparisons between the PC's keyboard and IBM's own electric typewriter layouts--typists converting to PC use were irritated that IBM had made the PC keyboard "worse" than their own typewriter keyboards, which certainly seems like a reasonable complaint to me!
Closeup photo of an original IBM PC/XT keyboard, showing its layout. Here are some of the main issues with this layout, when it is contrasted to more modern configurations (note that while you may not care all that much about this very old design-- and I don't blame you--reading this list will help you understand the changes made in later designs):
Cramped Physical Grouping: Just looking at it, you can see that it is a very "cramped" layout. All of the keys except the function keys are physically contiguous, giving the layout a very "busy" appearance. This is made worse by the fact that so many keys are of odd sizes, and there is no clear vertical "dividing line" for the eye between the main typing area and the numeric keypad. Even the function keys are not separated very much from the rest of the layout. Overall, it looks like a "jumble of keys". This may seem a trivial matter but has an impact on those learning to use the PC. Poor
84-Key AT Keyboard
Looking at the number of issues regarding the original 83-key XT keyboard, you can see that it's a pretty long list. Of course, in the early 1980s you didn't really have a lot of options. :^) Still, over time, IBM received a lot of complaints about the first keyboard design and eventually made improvements to it. The first evolution of the keyboard was the 84-key keyboard layout introduced with the first IBM PC/AT. Unsurprisingly, this is sometimes called the AT Keyboard.
Closeup photo of an IBM PC/AT clone keyboard, showing the 84-key keyboard layout. (The LED indicators are above the numeric keypad and not shown in this photo.)
There are several definite improvements with this layout, compared to the 83-key keyboard:
Better Physical Grouping: The keyboard has three distinct key physical groups, with the numeric keypad placed distinctly to the right. The three groupings have clean vertical lines. The numeric keypad has been reorganized. Overall, the keyboard has a much more organized and understandable appearance. Improved
However, many of the layout issues with the original design remained. The biggest concern that remained unaddressed was the continued sharing between the numeric keypad, and the cursor and navigation keys. The function keys are still on the left-hand side, and the
Some PC users also believe that this keyboard layout took one step backwards, in relocating the
This keyboard was changed internally from the PC/XT model as well. The interface was made bidirectional, allowing the system to send commands to the keyboard, and enabling the control of the new LED indicators. The signaling and interface protocols created with this first PC/AT keyboard are still used today, even though the 84-key layout is no longer used, having been replaced by the "Enhanced" 101-key keyboard.
101-Key "Enhanced" Keyboard
In 1986, IBM introduced the IBM PC/AT Model 339. Included in this last AT-family system was the new Enhanced 101-key keyboard. Little did IBM realize at the time, perhaps, but this 101-key keyboard would become the de-facto standard for keyboards for the next decade and beyond. Even today's Windows keyboards and fancy variants with extra buttons and keys are based on this layout.
Closeup photo of a 101-key "Enhanced" keyboard, showing the layout of the various key groups. Contrast this layout to that of the 104-key "Windows" keyboard.
The "Enhanced" keyboard was electrically the same as the 84-key AT keyboard, but featured a radically redesigned key layout. The major changes included these:
Dedicated Cursor and Navigation Keys: Finally, separate keys were provided for cursor control and navigation. This enabled the numeric keyboard to be used along with the cursor and navigation keys. The cursor keys were also made into an "inverted-T" configuration for easier switching between "Up" and "Down" with a single finger. Relocated Function Keys: The function keys were moved from the left-hand side of the keyboard to a row along the top, and divided into groups of four for convenience. While many users had been asking for this, they found that sometimes the grass really isn't greener on the other side of the fence, as I discuss below... Relocated
Compared the 84-key keyboard the Enhanced keyboard layout was perceived by most users to be far superior. It was an immediate hit despite its one obvious inferiority to the AT keyboard: the smaller main
Many PC users, after having complained for years about changes they wanted made to the PC keyboard layout, found they weren't all that happy with them once their wish was granted! Having never complained about the issues that were changed with the Enhanced keyboard myself, I found some of the changes quite frustrating--and I later discovered that I was not alone. My personal beefs with this layout involve the locations of the following:
Left
Despite these limitations, the 101-key keyboard remains the standard (actually, the 104-key Windows keyboard is the standard now, but the two layouts are nearly identical). Of course, countless variations of the basic design exist. A common modification is to enlarge the
Keyboard Layout
The layout of a keyboard refers to the organization of its keys; it is important for many reasons. For starters, typing with speed and accuracy requires familiarity with the locations of the various keys, and changing between keyboards of different types can be difficult for many touch typists. Some people also find certain key configurations easier to use than others in general, and some PC users have special needs or requirements that can best be met by special keyboard layouts.
1 .Qwerty layout
2 .Dvorak-Dealey layout
A computer keyboard uses a standard layout for the keys, known as QWERTY. Learn where this idea comes from and why it has remained the same for more than a century.
QWERTY Keyboard
Look only at the letter keys and start reading from the top left. It starts off like this: Q - W - E - R - T - Y. This is also referred to as QWERTY, pronounced 'kwirti.' Now look at another device with a keyboard - perhaps another computer, a smart phone or a tablet. Devices like tablets don't have a physical keyboard, but if you use an application in which typing is needed, a virtual keyword comes up. Take a look at the layout of the letters. QWERTY again!
Typical QWERTY sequence on a keyboard Now that you know that QWERTY rules supreme, let's take a look at its history and why it has remained the same for so long.
History
The original QWERTY layout was developed by Christopher Latham Sholes. He filed a patent application in 1867 for an early version of a typewriter. After a few modifications, his patent in 1878 looked like the image below. You will notice some differences with today's keyboards, but most of the letters are exactly where they are today. See if you can spot some of the small differences.
QWERTY layout in the original patent application of 1878
So why QWERTY and not just ABCDE etc.? To understand this, you need to remember that, at the time, the layout was developed for mechanical typewriters. These have keys, just like a modern-day keyboard, but when you press a key, a mechanical arm is moved to type a character on a piece of paper. When you start typing fast, these arms can jam easily. So, what was Sholes' big idea? He examined common letter combinations in the English language and made sure to place these letters far apart from each other. This resulted in fewer jams and, in effect, more efficient typing; however, by today's standards, the QWERTY layout actually slows down typing, since jamming mechanical arms are no longer an issue.
The QWERTY layout became popular when the Remington company adopted it for its typewriters. Want to know another peculiar detail? Type out the word 'typewriter.' Notice how your fingers only use the top row of letters? That's no coincidence.
Another detail to consider is how the keys are not on a perfect grid, but slightly slanted diagonally. This also goes back to the mechanical arms of typewriters. Keys had to be offset slightly to avoid the mechanical arms running into each other. Again, this is no longer necessary for modern-day keyboards, but the slanted design has endured.
Alternatives and Variants
By modern standards, the QWERTY keyboard is not the most efficient. Remember that it was actually designed to slow typing down! Several alternatives have emerged but never replaced QWERTY as the standard. Back in 1936, August Dvorak came up with a simplified layout that claimed to use less finger motion, increase typing speed, and reduce errors. Modern operating systems do provide support for the Dvorak layout, but the actual keyboards are not very common.
Since QWERTY was developed for the English language, slight modifications have been developed for other languages. They include QWERTZ (for German and other Central European languages) and AZERTY (for French). These are really minor modifications created by moving a few keys around. For languages that use a completely different character set, entirely different keyboards have been developed. Have a look at the one below for Turkey. Let's see how fast you can type 'typewriter' on this one.
Dvorak layout
Though Dvorak may sound like another string of letters, it’s in fact the surname of this keyboard layout’s inventor, August Dvorak. The inventor felt, when he patented his design in 1936, that QWERTY was uneconomical and uncomfortable—and therefore wasn’t the perfect layout. Dvorak believed that his layout was more efficient, and studies seem to agree.
People using QWERTY keyboards only make 32 percent of strokes on the “home row” (where your fingers naturally rest on a keyboard). For Dvorak, that rises to 70 percent. And likewise, most people are right handed: Dvorak accounts for that, making more than half the strokes right handed. QWERTY calls on people to use their left hands more. But save for a few eager practitioners, Dvorak is the lesser-known layout.
Block Diagram of Keyboard Controller:
What is Keyboard Controller? Keyboard Controller is a an electronic device or IC chip that is used to interface keyboard with the computer or system. It is the main controlling device of keyboard. It reads signals coming from the keyboard matrix and interpret them according to the main program written in its memory. It has its own primary memory like ROM for storing programs. We can also re-program the ROM of the Keyboard controller if we need to.
But mostly these programs are pre-written by Product vendors. Before deeply digging into the construction and working of keyboard controller, first let us have a look at the working of the Basic Keyboard or Key switches. By reading this you will know how our pressed keys are acknowledged to the computer or how our computer knows that we pressed a key on the keyboard.
Construction and Working of a Keyboard: Basically, a keyboard consists of a matrix of rows and columns. The switches are fabricated on these matrices in such a away that when we press a specific key, a specific row and column got short circuited and this will let the keyboard controller know that which key is being pressed. The corresponding signals for those specific rows and columns are sent to keyboard controller. It processes that incoming signal and send the signal to the main CPU. Thus CPU gets the idea that which key is pressed and then display that specific key.
Construction and Working of Keyboard Controller: Keyboard controllers usually comes in the form of IC chips. Most popular Keyboard controllers are Intel 8042 and Intel 8048. A keyboard controller consists of a RAM, ROM, Processor and some other Input/Output registers. The program, according to which, the controller works is saved in the ROM. RAM is used as a temporary storage for storing temporary variables or data. The construction diagram of Keyboard Controller is given below: As we can see from the diagram. There are three main blocks of a keyboard controller. These are :
Random Access Memory (RAM) Read Only Memory (ROM) Processor Explanation of each block is given below: Processor: The processor is used to convert the incoming Row-column signals into scan codes. These scan codes are then saved in the Output buffer. Then these scan codes are sent to the CPU or the system by the output buffer. The output buffer is a read only resister having size of 8 bits. If we keep key pressed for a long time (for example: more than half a second) then the processor also provides the feature to repeat the scan codes. The Keyboard having such ability is known as Type Matic Keyboards. Today, all keyboards have such facilities. This feature is also known as 'Auto Repeat Facility'.
There are two other buffers along side output buffer. These are : Status register Input Buffer Register Status Register: As its name suggests it shows status of Keyboard controller to the main system or CPU. It is also an 8 bit register. It is read/write register. If main CPU wants to re- program the Keyboard Controller then it can send a control command to the status register.
Input Buffer Register: It is a register which contains both data and commands. It is an 8 bit Write only register. It have two input/output ports 60H and 64H. Port 60H is used for transmission of data, that is if any byte arrives through this port then it will be treated as data byte. The other Port 64H is used for commanding the controller. If a byte is received through this port then it will be treated as instruction or command.
Read Only Memory(ROM):As stated before, ROM chip is the primary memory of the Keyboard controller where the program is stored permanently. The Keyboard Controller works according to the program written in its memory i.e. Read Only Memory (ROM).
Keyboard Switch: Computer keyboards can be classified by the switch technology that they use. Computer alphanumeric keyboards typically have 80 to 110 durable switches, generally one for each key. The choice of switch technology affects key response (the positive feedback that a key has been pressed) and pre travel (the distance needed to push the key to enter a character reliably). Newer keyboard models use hybrids of various technologies to achieve greater cost savings.
Underneath each key is a switch. When the key is pressed, the switch closes. Three types of switches are used in keyboards: Mechanical
Each key on a mechanical-switch keyboard contains a complete switch underneath. Each switch is composed of a housing, a spring, and a stem. Switches come in three variants: linear with consistent resistance, tactile with a non-audible bump and clicky, a tactile with an audible click. Depending on the resistance of the spring, the key requires different amounts of pressure to actuate. The shape of the stem varies the actuation distance and travel distance of the switch.The amount of sound produced by actuation can also be changed. Mechanical keyboards allow for the removal and replacement of keycaps. Mechanical keyboards also have a longer lifespan than membrane or dome-switch keyboards, with an expected lifespan of 50 million clicks per switch for Cherry MX switches, while switches from Razer have a rated lifetime of 60 million clicks per switch. The major current mechanical switch producer is Cherry. Alps Electric, a former major producer, ended production in the early 2000s, but Alps style switches continue to be made by others companies as Matias, Xiang Min(XM), Tai-Hao (APC) and Hua-Jie (AK). Others switch manufacturer are Gateron, Kaihua (Kailh), Gaote(Outemu), Greetech, TTC and Omron.
Capacitive
In this type of keyboard, pressing a key changes the capacitance of a pattern of capacitor pads. The pattern consists of two D-shaped capacitor pads for each switch, printed on a printed circuit board (PCB) and covered by a thin, insulating film of solder mask which acts as a dielectric. Despite the sophistication of the concept, the mechanism of capacitive switching is physically simple. The movable part ends with a flat foam element about the size of an aspirin tablet, finished with aluminum foil. Opposite the switch is a PCB with the capacitor pads. When the key is pressed, the foil tightly clings to the surface of the PCB, forming a daisy chain of two capacitors between contact pads and itself separated with thin solder mask, and thus "shorting" the contact pads with an easily detectable drop of reactance between them. Usually this permits a pulse or pulse train to be sensed. Because the switch doesn't have an actual electrical contact, there is no denouncing necessary. The keys do not need to be fully pressed to be actuated, which enables some people to type faster. The IBM Model F keyboard is mechanical-key design consisted of a buckling spring over a capacitive PCB, similarly to the later Model M keyboard that used a membrane in place of the PCB. The most known company for their capacitive (electrostatic) switching technology is Topre Corporation from Japan. Unfortunately though, their products are not available in large parts of the world. Membrane
There are two types of membrane-based keyboards, flat-panel membrane keyboards and full-travel membrane keyboards: Flat-panel membrane keyboards are most often found on appliances like microwave ovens or photocopiers. A common design consists of three layers. The top layer has the labels printed on its front and conductive stripes printed on the back. Under this it has a spacer layer, which holds the front and back layer apart so that they do not normally make electrical contact. The back layer has conductive stripes printed perpendicularly to those of the front layer. When placed together, the stripes form a grid. When the user pushes down at a particular position, their finger pushes the front layer down through the spacer layer to close a circuit at one of the intersections of the grid. This indicates to the computer or keyboard control processor that a particular button has been pressed. Generally, flat-panel membrane keyboards do not produce a noticeable physical feedback. Therefore, devices using these issue a beep or flash a light when the key is pressed. They are often used in harsh environments where water- or leak-proofing is desirable. Although used in the early days of the personal computer (on the Sinclair ZX80, ZX81 and Atari 400), they have been supplanted by the more tactile dome and mechanical switch keyboards. Full-travel membrane-based keyboards are the most common computer keyboards today. They have one-piece plastic keytop/switch plungers which press down on a membrane to actuate a contact in an electrical switch matrix.
Hall-effect keyboard Hall effect keyboards use magnets and Hall effect sensors instead of switches with mechanical contacts. When a key is depressed, it moves a magnet that is detected by a solid-state sensor. Because they require no physical contact for actuation, Hall-effect keyboards are extremely reliable and can accept millions of keystrokes before failing. They are used for ultra-high reliability applications such as nuclear power plants, aircraft cockpits, and critical industrial environments. They can easily be made totally waterproof, and can resist large amounts of dust and contaminants. Because a magnet and sensor are required for each key, as well as custom control electronics, they are expensive to manufacture.
Opto electronic switch
•Opto electronic switch are based on optical and electronic device. •This types of switches have a LED which generates light when proper electric power is applied. •Opposite to the LED, a photo-transistor is such that it allows the current flow in the circuit, as long as light is applied to it. •When the light following to the photo-transistor is removed, it will no longer allow the current to pass through it. •In this type of switch, when the key is not pressed, the light from LED falls onto the photo- transistor. •This makes the current to flow through the photo-transistor and produces a very low voltage at the output Vout.
In most of the keyboards two types of faults are found.
The main fault is the non operation of the keyboard.
This can be due to 1. Broken connections between key board and main processor 2. In - compatibility 3. Other hardware problems like problems in keyboard controller IC or main system etc.
The second keyboard fault arises because of:-
1. The broken keys or some times stuck keys.
Keyboard prints unwanted characters or some of the keys may stop working. This happens because of key matrix problem or scanning circuit problems.
All the above problems can be resolved in most of the cases.
Trouble shooting
Trouble shooting methods for common faults of computer keyboard :
Non operation of keyboards
If a keyboard is not working , it may be because of broken connection between keyboard and main system. So first of all check the connection behind system and make it tight. Also check the cable connecting the key board and main system. If it is OK and the keyboard is still not working then check the compatibility switch behind the keyboard. It is very much possible that you have selected an XT mode for an AT system. Most of the system contain keyboard lock on front panel. Check it also it may be locked. If it is so, unlock the keyboard. Though in most of the cases during boot the system informs you that key board is locked.
Broken or stuck keys
Some times it happens that one or two keys are not working while rest are working properly. This may happen because of broke or stuck keys. This problem mostly occurs in mechanical key switch. Most of them use a spring or a rubber dome to keep the keys from being " ON " all the time. First of all check this spring or rubber dome whichever is there. The spring can be broken or may stuck in. If it is simply stuck in, try to pull it up from your fingers or a clip. If it is just stuck , this job may solve your problem but if the spring is broken or rubber dome is damaged then you have no option other then to replace the key. For this job open the keyboard and solder a new switch at its position. Now the keyboard may be tested on the system.
If the problem is of stuck keys then it can be because of dirt on the switches. Just clean the keyboard properly. For this remove the key cap and add some lubricant. Press the key 3-4 times. Some times the addition of contact cleaner will also clean the contact dirt.
Some keys working and some not
Some times it happens that a set of key is working while all other key are working. This may happen either because of broken connection/lines or because of the problem of row decode or decode logic. For removing this trouble open the keyboard and check it for broken lines , dry soldering and loose contacts. If possible clean all keys and reassemble the keyboard. If it still not working properly check keyboard driver along with dismantle and reassemble the keyboard.
Try applying all the above discussed methods and still your keyboard does not work properly then you have no way other than changing the keyboard. There are not very costly so you can easily replace it with a new one.
Computer mouse: A computer mouse is a handheld hardware input device that controls a cursor in a GUI and can move and select text, icons, files, and folders. For desktop computers, the mouse is placed on a flat surface such as a mouse pad or a desk and is placed in front of your computer. The picture to the right is an example of a desktop computer mouse with two buttons and a wheel.
What are the uses of a mouse?
Below is a list of each of the computer mouse functions that help a user use their computer and gives you an idea of all of the things a mouse is capable of doing. 1. Move the mouse cursor - The primary function is to move the mouse pointer on the screen. 2. Open or execute a program - Once you've moved the pointer to an icon, folder, or other object clicking or double clicking that object opens the document or executesthe program. 3. Select - A mouse also allows you to select text or a file or highlight and select multiple files at once. 4. Drag-and-drop - Once something is selected, it can also be moved using the drag- and-drop method. 5. Hover - Moving the mouse cursor over objects with additional hover information can help discover the function of each object on the screen. For example, hover the mouse over the hover link to see an example. 6. Scroll - When working with a long document, or viewing a long web page, you may need to scroll up or down. To scroll, use the mouse wheel, or click and drag the scroll bar. 7. Perform other functions - Many desktop mice also have additional buttons that can be programmed to perform any function. For example, many mice have two side buttons on the thumb portion of the mouse the button closest to the palm can be programmed to go back on web pages. How has the mouse increased computer usability?
By using a computer mouse, the user doesn't have to memorize commands, such as those utilized in a text-based command line environment like MS-DOS. For example, in MS-DOS a user would have to know the cd command and dir command and type the commands on the keyboard to navigate to a directory (folder) and view the files inside. Whereas a Windows user only has to double-click to open a folder and see its contents.
What are the parts of a computer mouse?
The parts of a computer mouse can vary by the type of computer mouse. Below is a general overview of the parts found on most computer mice. Buttons Today, almost all computer mice have at least two buttons, a left button and right button for clicking and manipulating objects and text. In the past, there have been mice with only one button. For example, many of the early Apple computer mice only had one button. Ball, Laser, or LED A desktop mouse may contain a ball and rollers if it is a mechanical mouse or a laser or LED if it is an optical mouse. Each of these components are used to track the movement and move the mouse cursor on the screen. Mouse wheel Today's desktop computer mice also usually include a mouse wheel that allows you to scroll up and down on a page. Tip: Instead of rolling the wheel if you push in on the wheel it can be used as a third button. Circuit board To take all the signal information, clicks, and other information being created by the mouse and input it to the computer it must also have a circuit board with integrated circuits. Cable or wireless receiver For a corded mouse, it also includes a cable with a plug that connects to the computer. Today, most corded mice connect to the USB port. If your computer has a wireless mouse, it needs a USB wireless receiver to receive the wireless signal and input it into the computer. Other parts If you're using a laptop, some of the above components mentioned earlier are not required. For example, a touchpad does not use a ball, laser, or LED to control movement it uses your finger on the touchpad. Other parts include a ball for trackball mice, extra buttons that may be on the thumb side of the mouse, and nubs that may be used with laptop mice.
List Of Common Mouse Problems Here’s a list of the most common mouse problems along with their causes and what you can do about them:
1. Mouse pointer does not move smoothly. Main cause: Accumulation of dust at the bottom of the mouse surface. Solution: Clean the dust at the bottom of the mouse surface. Clean or change your mousepad.
2. Mouse pointer freezes. Main cause: High CPU usage or hanging of some application.
Solution: Wait a few seconds and see if the mouse starts to respond. If it doesn’t respond after a minute or so, try launching the task manager from your keyboard (Ctrl + Shift + Esc for Windows, Command + Option + Escape for Mac). If that still doesn’t work, it’s time to restart your computer.
3. Mouse doesn’t work at all. Main cause: Loose connections or the mouse connector is connected to the wrong port.
Solution: Check the physical connection to make sure that the mouse is properly connected to its rightful port. Still not working? Time to a buy a new mouse, then.
4. Mouse pointer is too fast or too slow.
Main cause: Settings configuration.
Solution: Open your Control Panel. Go to Mouse -> Pointing Devices -> Set mouse speed.
5. Problem with double click. Main cause: Settings configuration.
Solution: Open your Control Panel. Go to Mouse -> Pointing Devices -> Set mouse double click speed. Still not working? Buy a new mouse.
Light Pen:
A light pen is a pointing device. It is used to select a displayed menu option on the Cathode Ray Tube (CRT). It is a photosensitive pen-like device. It is capable of sensing a position on the CRT screen when its tip touches the screen. When its tip is moved. over the screen surface, its photocell sensing element detects the light coming from the screen and the corresponding signals are sent to the processor.
A light pen can also be used for graphics work. A user can draw directly on the CRT screen with the light pen if the computer system is provided with Computer Aided Design (CAD) package. A light pen may refer to any of the following: 1. A light pen is a light-sensitive pointing input devicecommonly used to select or otherwise modify text or data on a screen. Used with a CRT monitor, these devices were an early form of manipulating and highlighting data on the screen. In the picture is an example of a woman using a light pen to highlight text on the screen. Light pens were originally developed around 1955and in the 1960s, they became more commonly used with graphics terminals, like the IBM 2250. In the 1980s, light pen usage expanded to home computers, like the BBC Micro computer. Some graphics cards also included a connection for a light pen. Today, light pens are no longer used due to the invention of touch screens. 2. The term light pen may also refer to a pointing input device utilizing a light that is commonly used during a presentation. The light pen can be a very focused flashlight- type of device or a laser pointer, allowing a user to direct viewers' attention to a specific area, like a picture or text, in the presentation.
Working of Light Pen : The light pen, with its interface and software, makes a time measurement that is translated into X-Y coordinates representative of a position on the monitor. The light pens contain a lens and a photodetector located at its tip. When the electron beam that sweeps the monitor strikes the phosphor within the light pen’s field of view, the light emitted by the phosphor is focused through the lens and onto the photodetector.
The position of the beam is tracked by the horizontal and vertical counted, which relay this information to a register. This cycle is repeated for every frame produced by the electron beam. By noting when a scan goes by the measuring the interval between scan lines or entire screen refreshes an accurate position of the photodetector on the screen is determined. The light pen software generates X-Y vectors corresponding to a point on the screen, which may be used to make a selection by activating a switch on the light pen.
Joystick: In computers, a joystick is a cursor control device used in computer games and assistive technology . The joystick, which got its name from the control stick used by a pilot to control the ailerons and elevators of an airplane, is a hand-held lever that pivots on one end and transmits its coordinates to a computer. It often has one or more push-buttons, called switches, whose position can also be read by the computer.
How do joysticks work? Joystick is an innovative product that takes the movement of something entirely physical – the movement of the human hand using it, and converts the movements for use in a computer or to control machines. It works on a simple principle where the machine accepts the hand movement with the help of the sensors and converts it into a mathematical code, which then moves the virtual body in the computer in the same way.
The joystick though looks like simple equipment is a great invention that has added new dimensions of fun and excitement to the world of gaming. Today, a number of games are available that work on the joysticks where the individual is able to manipulate the virtual image and make them move in any direction by a simple flick of the joystick.
The working of joystick is simple. It is based on the principle of conversion of physical movement into a digital signal which when accepted by the device produce same results on the screen. The joystick starts working only when it is connected to the computer or the gaming device. While playing the game, every time the user makes a movement on the joystick, the wires in the device connects a circuit with one another and the computer to produce the same movement in the virtual body in the game or the application.
With good joysticks, the flow of the translation can be so flawless that one can completely forget about the real world and feel like a part of the virtual game. The joystick makes the player feel engaged in the game and help them relate directly with the virtual world. With the technological advancements, new designs of the joystick are coming into the market, which is making games all the more interesting and interactive. All one needs to do is to buy a good joystick and connect with the computer or gaming device. Follow the given instructions to completely calibrate the joystick and start enjoying the virtual world of reality.
Scanner:
A scanner is a device that converts images to a digital file and you can use with your computer. There are many different types of scanners: Film scanners, Flatbed scanners, and Drum scanners
Dedicated Film scanners
This type of scanner is sometimes called a slide or transparency scanner. They are specifically designed for scanning film, usually 35mm slides or negatives, but some of the more expensive ones can also scan medium and large format film. These scanners work by passing a highly focused beam of light through the film and reading the intensity and color of the light that emerges.
Flatbed scanners
This type of scanner is sometimes called a reflective scanner. They are designed for scanning prints or other flat, opaque materials. These scanners work by shining white light onto the object and reading the intensity and color of the light that is reflected from it. Some Flatbed scanners have available transparency scanning adapters, but in most cases these are not as well suited to scanning film as a dedicated film scanner.
Drum scanners
These professional devices are pretty much out of the reach of the individual photographer. To use a Drum scanner, the original is taped to a rotating clear plastic Drum and scanned as the Drum rotates. Drum scans have the highest quality but are labor intensive and very expensive.
Drum scanner
CCDs vs. Photomultipliers
Most dedicated film scanners, Flatbed scanners, use light sensing elements called CCDs (Charge Coupled Devices) to measure light. CCDs are relatively inexpensive, compact, and efficient. Most high end Drum scanners use photomultiplier tubes to measure light. Photomultipliers, while larger and more expensive to design around, do offer superior dynamic range. Thus a scanner that uses photomultiplier tubes can extract more detail from very dark shadow areas of a transparency. CCD scanners, while steadily improving in this area, are still prone to losing detail in deep shadow areas.
Photomultiplier tube (PMT) Scanner characteristics
There are many different types of scanners, each one has its own characteristics. The quality of the digital images, can obtain from a scanner depend on many factors:
Resolution
Resolution is a measurement of how many pixels a scanner can sample in a given image. Resolution is measured by a grid. Think of a chessboard, with eight squares along each side. The resolution of that chessboard would be 8 x 8. If the chessboard had 300 squares along each side, its resolution would be 300 x 300. (the typical resolution of an inexpensive desktop scanner today).
That scanner samples a grid of 300 x 300 pixels for every square inch of the image, and sends a total of 90,000 readings per square inch back to the computer. With a higher resolution, you get more readings; with a lower resolution, fewer readings. Generally, higher resolution scanners cost more and produce better results.
There are two ways of measuring resolution:
1– Optical Resolution
A scanner's optical resolution is determined by how many pixels it can actually see. For example, a typical Flatbed scanner will use a scanning head with 300 sensors per inch, so it can sample 300 dots per inch (dpi) in one direction. To scan in the other direction, it will move the scanning head along the page, stopping 300 times per inch, so it can scan 300 dpi in the other direction as well. This scanner would have an optical resolution of 300 x 300 dpi. Some manufacturers stop the scanning head more frequently as it moves down the page, so their machines have resolutions of 300 x 600 dpi or 300x1200 dpi.
Don't be fooled; what really counts is the smallest number in the grid. You can't get more detail by scanning more frequently in only one direction.
2– Interpolated Resolution
The other thing to watch out for is claims about interpolated (or enhanced) resolution. Unlike optical resolution, which measures how many pixels the scanner can see, interpolated resolution measures how many pixels the scanner can guess at. Through a process called interpolation, the scanner turns a 300 x 300 dpi scan into a 600 x 600 dpi scan by inserting new pixels in between the old ones, and guessing at what light reading it would have sampled in that spot had it been there. This process almost always diminishes the quality of the scan, and should therefore be avoided. It can also be accomplished by almost any image editing software, so it doesn't really add to the value of the scanner. Unless you plan to scan line art at very high resolutions (more on that later), ignore claims of interpolated resolution.
Bit Depth: When a scanner converts something into digital form, it looks at the image pixel by pixel and records what it sees. That part of the process is simple enough, but different scanners record different amounts of information about each pixel. How much information a given scanner records may be measured by its bit depth. The simplest kind of scanner only records black and white, and is sometimes known as a 1-bit scanner because each bit can only express two values, on and off. In order to see the many tones in between black and white, a scanner needs to be at least 4-bit (for up to 16 tones) or 8-bit (for up to 256 tones). The higher the bit depth for the scanner, the more accurately it can describe what it sees when it looks at a given pixel . This, in turn, makes for a higher quality scan.
Most color scanners today are at least 24-bit, meaning that they collect 8 bits of information about each of the primary scanning colors: red, blue, and green. A 24-bit unit can theoretically capture over 16 million different colors, though in practice the number is usually quite smaller. This is near-photographic quality, and is therefore commonly referred to as "true color" scanning.
An increasing number of manufacturers are offering 30-bit, 36-bit or 48-bit scanners, which can theoretically capture billions of colors. The only problem is that very few graphics software packages can handle anything larger than a 24-bit scan, because of limitations in the design of personal computers. When a software program opens a 30-bit, 36-bit or 48-bit image, it can use the extra data to correct for noise in the scanning process and other problems that hurt the quality of the scan. As a result, scanners with higher bit depths tend to produce better color images.
Dynamic Range
Another important criteria for evaluating a scanner is the unit's dynamic range, which is somewhat similar to bit depth in that it measures how wide a range of tones the scanner can record. Dynamic range is measured on scale from 0.0 (perfect white) to 4.0 (perfect black), and the single number given for a particular scanner tells how much of that range the unit can distinguish.
Most color Flatbeds have difficulty perceiving the subtle differences between the dark and light colors at either end of the range, and tend to have a dynamic range of about 2.4. That's fairly limited, but it's usually sufficient for projects where perfect color isn't a concern.
For greater dynamic range, the next step up is a top-quality color Flatbed scanner with extra bit depth and improved optics. These high-end units are usually capable of a dynamic range between 2.8 and 3.2, and are well-suited to more demanding tasks like standard color prepress.
The CCD sensors used in less expensive scanners have a smaller dynamic range than the photomultiplier tubes used in the high-end Drum scanners used for commercial prepress work. This can lead to loss of shadow detail, especially when scanning very dense transparency film. Where scanners have the most problem is usually extracting detail from the darkest parts of transparencies. Scanner vendors frequently report a DMAX number with is the maximum optical density the scanner is capable of distinguishing from solid black.
Density is a logarithmic scale, so a density of 4.0 means that only 0.0001 of the light (or 0.01%) passes through the film. Transparency film typically has a DMAX of around 4.0, so a scanner with a DMAX of 3.4 will lose some deep shadow detail.
While a high dynamic range is no guarantee of good scanning results (many other factors come into play), it is generally an indication that the scanner manufacturer is striving to please educated buyers by producing a higher-quality product. All other things being equal go with the scanner that offers the higher dynamic range.
DIGITIZER INTRODUCTION
A Digitizer is a device which converts analog information into a digital form. You can easily do your signatures using this pen or styles or pen on the digitizer and it is the job of digitizer or change your signatures in bit map and send them to computer for storage. From there , whenever needed the same shape can be regenerated. Digitizer are very accurate devices. They are available in many sizes. The most common size are 6 into 8 inch and 12 into 18 inch. The cost of a digitizer increasers with increase in size. Thus bigger size digitizer are very costly. The styles used with digitizer looks like an ordinary pen. You can hold it in the same way and can make artistic strokes on the digitizer using it . Whatever strokes you will apply on the digitizer , the same can be seen on the screen
Working of an Digitizer :
The working of a digitizer in similar to that of a mouse with some major differences. Actually the input from a mouse is relative to the cursor position on the screen and that is why if you draw a line with a mouse and then pick it up and move to a different place on desk you will find that the input continues from the last position of the cursor on the screen , where it was. But in case of a digitizer each position on the tablet relates to a specific position on the screen. So it traces the existing drawing more accurately and it can easily create original drawing such as architectural drawing with precise dimensions. The styles draws directly on the tablet and its movements are captured and translated into a corresponding drawing on the computer. A puck or cursor can also be used instead of styles. In both the cases the exact positions of drawing device is detected by the tablet in terms of coordinates and is sent to the computer.
Unit 5 Cathode Ray Tube – CRT
Computer technology is going to see major advances in sophisticated 3 dimensional modeling and image processing; the users will see desktop computers with the computational power of today’s super-computers. Even graphics capabilities would be available to the average user at a reasonable cost. To make this, an ultra high resolution monitors will be required. There are different display systems like cathode ray tubes (CRTs), liquid crystal displays (LCDs), electroluminescent displays (ELDs), plasma displays and light emitting diodes (LEDs) are available in the present technology. Here we are going to discuss about the Cathode Ray Tube (CRT).
Working Principle of CRT: When the two metal plates are connected to a high voltage source, the negatively charged plate called cathode, emits an invisible ray. The cathode ray is drawn to the positively charged plate, called the anode, where it passes through a hole and continues travelling to the other end of the tube. When the ray strikes the specially coated surface, the cathode ray produces a strong fluorescence, or bright light. When an electric field is applied across the cathode ray tube, the cathode ray is attracted by the plate bearing positive charges. Therefore a cathode ray must consist of negatively charged particles. A moving charged body behaves like a tiny magnet, and it can interact with an external magnetic field. The electrons deflected by the magnetic field. And also when the external magnetic field is reversed, the beam of electronics is deflected in the opposite direction. In a cathode ray tube, the cathode is a heated filament and it placed in vacuum. The ray is a stream of electrons that naturally pour off a heated cathode into the vacuum. Electrons are negative. The anode is positive, so it attracts the electrons pouring off the cathode. In a TV’s cathode ray tube, the stream of electrons is focused by a focusing anode into a tight beam and then accelerated by an accelerating anode. This tight, high-speed beam of electrons flies through the vacuum in the tube and hits the flat screen at the other end of the tube. This screen is coated with phosphor, which glows when struck by the beam.
Operation of CRT Cathode Ray Tube (CRT) is a computer display screen, used to display the output in a standard composite video signal. The working of CRT depends on movement of an electron beam which moves back and forth across the back of the screen. The source of the electron beam is the electron gun; the gun is located in the narrow, cylindrical neck at the extreme rear of a CRT which produces a stream of electrons through thermionic emission. Usually, A CRT has a fluorescent screen to display the output signal. A simple CRT is shown in below.
The operation of a CRT monitor is basically very simple. A cathode ray tube consists of one or more electron guns, possibly internal electrostatic deflection plates and a phosphor target. CRT has three electron beams – one for each (Red, Green, and Blue) is clearly shown in figure. The electron beam produces a tiny, bright visible spot when it strikes the phosphor-coated screen. In every monitor device the entire front area of the tube is scanned repetitively and systematically in a fixed pattern called a raster. An image (raster) is displayed by scanning the electron beam across the screen. The phosphor’s targets are begins to fade after a short time, the image needs to be refreshed continuously. Thus CRT produces the three color images which are primary colors. Here we used a 50 Hz rate to eliminate the flicker by refreshing the screen.
Main parts of the cathode ray tube are cathode, control grid, deflecting plates and screen.
Cathode The heater keeps the cathode at a higher temperature and electrons flow from the heated cathode towards the surface of the cathode. The accelerating anode has a small hole at its center and is maintained at a high potential, which is of positive polarity. The order of this voltage is 1 to 20 kV, relative to the cathode. This potential difference creates an electric field directed from right to left in the region between the accelerating anode and the cathode. Electrons pass through the hole in the anode travel with constant horizontal velocity from the anode to the fluorescent screen. The electrons strike the screen area and it glows brightly. The Control Grid
The control grid regulates the brightness of the spot on the screen. By controlling the number of electrons by the anode and hence the focusing anode ensures that electrons leaving the cathode in slightly different directions are focused down to a narrow beam and all arrive at the same spot on the screen. The whole assembly of cathode, control grid, focusing anode, and accelerating electrode is called the electron gun. Deflecting Plates Two pairs of deflecting plates allow the beam of electrons. An electric field between the first pair of plates deflects the electrons horizontally, and an electric field between the second pair deflects them vertically, the electrons travel in a straight line from the hole in the accelerating anode to the center of the screen when no deflecting fields are present, where they produce a bright spot.
Screen This may be circular or rectangular. Screen is coated with special type of fluorescent material. Fluorescent material absorbs its energy and re-emits light in the form of photons when electron beam hits the screen. When it happens some of them bounces back just like bouncing of cricket ball from a wall. These are called as secondary electrons. They must be absorbed and returned back to cathode, if it is not so they accumulate near screen and produce space charge or electrons cloud. To avoid this, aquadag coating is applied on funnel part of CRT from inside.
Advantages of CRT 1. CRT’s are less expensive than other display technologies. 2. They operate at any resolution, geometry and aspect ratio without decreasing the image quality. 3. CRTs produce the very best color and gray-scale for all professional calibrations. 4. Excellent viewing angle. 5. It maintains good brightness and gives long life service. Features of CRT The use of CRT technology has quickly declined since the introduction of LCDs but they are still unbeatable in certain ways. CRT monitors are widely used in a number of electrical devices such as computer screens, television sets, radar screens, and oscilloscopes used for scientific and medical purposes.
Now you have got clear idea about the cathode ray tube and if any queries on this topic or on the electrical and electronic projects leave the comments below.
Computer Monitors - CRT, LCD, LED, Plasma & OLED Display Monitors : We all are familiar with the computer monitors. We spend time sitting in front of them for hours working, gaming or watching movies. A monitor is used to display the output of any computer system. A good display makes all the difference and no doubt enhances the user experience. The innovation in the display technologies has improved the quality of the display devices including monitors. Now the desktop computers are available with a variety of displays ranging from technologically obsolete CRT monitors to latest slim LCD, LED or OLED monitors.
Fig. 1: A Representational Image of Latest Slim LCD Monitor A computer monitor, technically termed as visual display unit is an output device that presents the information from the CPU on the screen working as an interface between CPU and the user. A cable connects the monitor to a video adaptor or video card which is set up on the motherboard of the computer. The CPU (Central Processing Unit) sends instruction to the video adaptor telling what needs to be displayed on the screen. The video adaptor converts the instructions into a set of corresponding signals and sends to the monitor. Monitor contains a circuitry that generates the picture on the screen from the set of signals.The major parameters that measure the performance of a monitor are luminance, contrast ratio, resolution, dot pitch, response time, refresh rate and power consumption. The common problem that arises in monitors is dead pixels, blurred screen, phosphor-burn, etc.
History
The first monitor dates long back in history. In the early stages of its evolution they were
known as Terminals,
Fig. 2: An Image of First Monochrome Monitor known as Video Display Terminals which were the boxy Video Display Terminals (VDTs). VDTs were monochrome monitors which used CRT (Cathode Ray Tube) technology. They were capable of working with any type of computer by connecting through a serial interface.
IBM’s CRT - IBM launched its first computer also known as a ‘three piece computer’ in 1981. It had three different units – CPU, monitor and keyboard separately. By 1984, IBM introduced the new CRT monitor with enhanced Color Graphics Adaptor (CGA) with 16 colors and a resolution of 640 x 350 pixels. In 1987 IBM started offering the Video Graphics Array as part of its new PCs which allowed 256 different colors and a resolution of 640 x 480 pixels. XGA and UXGA – A new technology named Enhanced Graphics Array or XGA was introduced in 1990 which allowed 16.8 million colors with a resolution of 800 x 600 pixels. The new monitors were now offering true colors that matched the human eye (human eye can detect 10 million different colors). Later the technology extended as UXGA, Ultra Extended Graphics Array which allowed 1600 x 1200 pixels.
In the 90s the LCD monitors came in the scene and gradually started competing with the CRT monitors. By the end of the 20th century, the CRT era was declining with the increasing popularity of Liquid Crystal Technology (LCD). This technology produces sharper images than the CRT monitors and the LCD monitors are significantly thinner having lower radiation emissions.
Few years’ back, LED displays came in the scene and they are gradually making its space in the market. LED technology has various advantages over LCD technology like better image quality, low power consumption, etc.
Display Technologies
Since the beginning of computer era, there have been a number of technologies used for the display of output. The major technologies are CRT, LCD, Plasma, LED and OLED displays.
1. Cathode Ray Tube (CRT) Monitors
These monitors employ the CRT technology to create a display. The CRT (also known as
picture tube) receives the
Fig. 3: A Diagram Illustrating CRT Technology Used in Monitors to Create Display signals through a cable and the signal is decoded by the display controller which finally appears on a phosphor screen. The detailed working is as following:
As shown in the image CRTs have a conical shape and there is an electron gun or cathode ray gun at the back end of the monitor and a phosphor screen in the front. The electron gun fires a stream of electrons towards the display screen through a vacuum tube. This stream of electrons is also known as cathode rays. At the middle of the monitor, there are magnetic anodes which are magnetized in accordance with the instruction from the display controller. When electrons (cathode rays) pass through the magnetic anodes, they are pushed or pulled in one direction or other depending on the magnetic field on the anodes. This directs the electrons towards the correct part of phosphor coating inside the display glass. When electrons strikes the phosphor coated screen passing through a mesh (shadow mask or aperture grill), the phosphor lights up making a displayable dot on the computer screen. There are three different colored phosphors (Red, Green and Blue) for each pixel and the color of the pixel depends on the phosphor on which the electrons strike. This image shows the color combination schematic for phosphor particles. The monitor that has a single electron gun has three different phosphors for each pixel. A cathode ray strikes to one or more of these phosphors and the corresponding colored pixel appear on the screen. However high quality monitors use individual electron gun for each color which improves the image quality. Distance for two same colored phosphors (for single electron gun monitors) is known as dot pitch. Lesser the dot pitch higher is the quality of monitors.
Aperture Grille v/s Shadow Mask
CRTs incorporate a metal sheet behind the display screen which affects the pixels on the
screen as well as
Fig. 5: An Image Showing Shadow Mask and Aperture Grill Incorporated in Cathode Ray Tube Monitors brightness on the screen. Shadow mask is an obsolete technology in which there is a metal sheet with millions of holes to pass electrons in order to hit the phosphor coating. The shadow mask covers the entire screen thereby protecting the phosphors from stray ions (due to vacuum) and also limits the strength of the rays reducing the brightness on the monitor.
Aperture grille is a mesh of wires rather than any metal sheet with holes in it. Although the grill is fragile, it allows a brighter display.
What is the resolution of the screen? – Resolution of a monitor tells how densely pixels are arranged on the screen. A combination of dot pitch and the viewable image area defines the maximum resolution of the screen. For example if a 21 inch monitor screen with a viewable area of 401mm x 298mm has a dot pitch of 0.26 mm, then its resolution is 1843 x 1370 pixels derived from a formula.
LCD Monitors
LCD, Liquid Crystal Display or also known as Liquid Crystal Diode is one of the most popular display technologies currently. LCD monitors are lightweight, compact, occupy less space, consume low power and are available in a reasonable price. Currently there are two types of LCD technology in use – Active matrix LCD technology or TFT and Passive matrix technology. The TFT technology is more reliable with better image quality while the passive matrix technology has a slower response and gradually becoming outdated.
As the name indicates, liquid crystals are the key elements of the display screen. By manipulating the crystal we can change the way they interacts with the light. There is a display controller in the monitor which receives the display signals from the video adaptor in the motherboard. The display controller controls two things – the electric signals to the liquid crystals and the back light. Structure of an LCD is shown in the below images (Also see how LCD works).
Fig. 7: A Diagram Showing Structure and Working of a LCD The liquid crystals used in the LCD are Twisted Nemantic (TN), a type of liquid crystals that are twisted at 90o with the surface. In this state, crystals allow the light to pass through the polarizer but on applying a voltage, they get untwisted and block the light to passing through the polarizer. The display controller starts the backlight that passes through the first piece of the glass. At the same time the display controller also send the electrical currents to the liquid crystal molecules to align and allowing the varying level of light to pass through the second piece of glass, forming the desired picture on the screen. In color monitors, each pixel is made of three liquid crystal cells fronted with red, green and blue filters. The light passing through the filtered screen forms the color what you see on the monitor. A wide range of colors are formed by varying the intensity of colored pixels.
The backlight is made of cathodes, and depending on the quality of the monitor, there may be a single cathode at the top or one at the top and one at the bottom, or two at the top and two at the bottom to improve the brightness and clarity of the monitor. These cathodes are diffused through a layer of plastic and diffusing materials. Resolution - Unlike the CRT monitors there is no complex equation for the dot pitch and the resolution. The resolution of a monitor is simply the number of pixels contained in the matrix. Typically a 17 inch monitor has a resolution of 1280 x 1024 pixels.
LED Monitors LED Monitors
In the previous decade, the display technology has changed significantly. LED displays are one of the latest developments.
Fig. 8 : A Representational Image of a LED Monitor In this field. LED monitors use light emitting diodes that acts as a performance booster in the monitors. Basically LED monitors are the LCD monitors with a LED backlight to power up the LCD panel. It means that LEDs are placed behind or around the LCD panel to enhance the luminosity and video definition of the monitor screen.
As we have seen in the above section of LCD monitors, they use a cold cathode light as backlight. In the LED monitors all the concepts are same except this backlight, which is replaced by LEDs.
There are three different types of LED monitors available based on the manner how the diodes are arranges in the monitor. These are – Direct LEDs, Edge LEDs and RGB LEDs. Both Edge and Direct LED display monitors use white diodes that are used to illuminate the LCD panel to produce the improved picture quality. The arrangement of LEDs in the monitor is shown in the below image: In the Direct LEDs display, white diodes are placed all over the panel to produce higher quality image while the Edge LEDs display uses LEDs only on the borders of the LCD panel. Direct LEDs are generally used in the production of high definition TV whereas the Edge LEDs is mainly used in the production of computer screens. RGB LEDs display is better among the three types of LED monitors as it uses red, green and blue diodes to produce the lifelike images with amazing contrast ratio.
LCD v/s LED Monitors / Why LED displays are better than the LCD displays:
Both types of monitors work on the same technology. LED monitors are LCD monitors with replaced cold cathode backlight to LED backlight. Here are the differences that make the LED displays better than the LCDs: · Contrast and Black level of the LED screen is better than the LCD screens because the liquid crystals cannot stop 100% of the backlight from cold cathode backlight and hence when the black screen is to be shown on the monitor, it is not completely black (as shown in the below image). But Edge LED screens perfectly show the black screen as there is no
backlight at all.
Fig. 10: An Image Showing Comparison of LCD and LED Monitor Contrast and Picture Quality
· Color accuracy for direct and edge LED displays and LCD displays are almost same but the RGB LEDs display has quite better color accuracy.
· When comparing the LED and LCD monitors with respect to viewing angle, they are same as backlight has nothing to do with viewing angles.
· LED displays consume less power. It is reported that they consume up to 40% less power than the LCD displays.
· LED displays do not use mercury (used in cathode lamps in LCD backlight) so they are environment friendly.
· The size of Edge and RGB monitors is slight thinner than the LCD monitors while prices are slight higher.
Plasma Monitors Plasma Monitors
Plasma technology is another technology used in display devices. The basic idea behind the
plasma technology is to Fig. 11: A Representational Image of Plasma Monitors Based on Plasma Technology Illuminate tiny colored fluorescent lights to create image pixels. Each pixel is made of three such fluorescent lights – red, green and blue lights. To create a wide range of colors, intensity of these lights is varied accordingly.
The heart of plasma displays is plasma which is basically a gas (generally Xenon and Neon) made up of free flowing electrons and ions. When the electrical current flows through the plasma, negatively charged particles move towards the positively charged area of the plasma and vice versa. This makes collisions which resultantly excite the gas atoms in the plasma and then release the energy as photons of
light.
Fig. 12: A Diagram Showing Working of the Plasma Technology There are millions of tiny cells filled with the gas like xenon and neon. They are positioned between two plates of glass known as front plate glass and rear plate glass. Two transparent electrodes covered by an insulating dielectric material and a magnesium oxide protective layer are also sandwiched between the glass plates on both sides of the cells on the entire screen.
When the CPU sends the signals to the Plasma monitor, the corresponding electrodes are charged which ionizes the gas in the intersecting cells by passing an electric current. Due to the collisions between the gas ions they release energy in the form of the photons of light which illuminate the respective cells. This process occurs thousands of times in a small fraction of second making the display faster. The released ultraviolet photons strike the phosphor material coated on the inner wall of the cell and hence phosphor electrons jump to the higher energy level. When the electron falls back to its normal state, it releases the energy as a visible light photon. Every pixel on the screen is made of three different colored phosphors – red, green and blue.
OLED Monitors
OLED, short for Organic Light Emitting Diode is the latest technology for display devices. As
the name suggests there
Fig. 13: A Representational Image of OLED or Organic Light Emitting Diode Monitors are some organic material (containing carbon, like wood, plastic or polymers.) that is used to convert the electric current into light. Since the LEDs are capable of producing different colored light, they are directly used to produce the correct color and there is no need of a backlight which saves power and space. With fast response time, wide viewing angles, outstanding contrast levels and perfect brightness, OLED displays are surely better than the existing other display technologies.
Fig. 14: A Diagram Illustrating Structure and Working of a OLED Display The heart of the OLED display is a stack of thin organic layers which is sandwiched between two conductors - a transparent anode and a metallic cathode, which in turn are sandwiched between two glass plates known as seal and substrate. The organic layer consists of a hole- injection layer, a hole-transport layer, an emissive layer and an electron-transport layer. When an appropriate voltage is applied, an electric current flows from cathode to anode through the organic layers. The cathode give electrons to the emissive layer of organic molecules while the anode takes equivalent electrons from the conducting layer of organic molecules. At the boundary of emissive and conductive layers, electrons and the holes are gathered. Here electrons are recombined with the holes by releasing energy in the form of photon of light. Hence the organic layer emits the light to produce the display. The color of the light depends on the type of organic molecules while the brightness depends on the amount of the current applied. By maximizing the recombination process in the emissive layer the output light can be improved in OLED devices. Thus the emissive layer is slightly doped with highly fluorescent molecules to enhance the electro-luminescent efficiency and control of color.
Advantage over conventional display technologies:
· The fabrication process is easy and the display devices are thinner than the conventional
display devices.
Fig. 15: An Image Showing Emissive Nature of OLED Monitors · Comparing it with the LCD devices, OLED displays can be viewed from different angles as they are “emissive” devices i.e. they emit light rather than modulating transmitted or reflected light.
· They do not use backlight.
· The driving voltage and total power consumption is low as comparing to other display technologies.
· The material used are eco friendly and do not use lead or other such material.
Difference Between Computer Monitor vs. TV Comparison Chart
Basis of Computer Monitor TV Distinction
Definition A software that helps to point the A software that transmits the seen visuals coming from the computer pictures and audio coming from the and the processing and working transmitter and used to broadcast carried out by the patron who reveals about coaching, information, maintains the machine. and leisure.
Usage An particular person has the chances Do not have such chances when the of working and ending completely television show display screen completely different duties. flashes.
Display Displays the packages coming from Displays the problems a person the channel itself and embody wants equal to movie, video, sound leisure, information and sports and completely completely different activities actions with help from a data. receiver.
Price Lesser Higher
Varieties They don’t want loads varieties and They have many kinds equal to LCD, have stayed related over time. LED, Cathode Ray and now 3D and HD.
VIDEO DISPLAY ADAPTERS
The video display adapter is a circuit card thatplugs into the personal computer to drive the monitor. Video adapter cards play a major role in how many colors are displayed and the speed with which display is updated. Common video adapters are:
1. MDA (Monochrome Display Adapter) 2. CGA (Color Graphics Adapter) 3. EGA (Enhanced Graphics Adapter) 4. VGA (Video Graphics Array) 5. SVGA (Super Video Graphics Array) 6. XGA (Extended Graphics Array)
Monochrome Display Adapter (MDA)
The monochrome display adapter (MDA) was the first display adapter available. It is designed to work with a monochrome transistor-transistor logic(TTL) monitor. It is a text-only system that cannot display graphics or color. The MDA uses a 9 x 14 dot character box that provides clean sharp characters. Because most of the software packages developed today, even word processing and spreadsheets, use graphics to some extent, the MDA is generally considered obsolete.
Color Graphics Adapter (CGA)
The color graphics adapter (CGA) was, at onetime, the most common graphics adapter available. It supports an RGB monitor with a maximum resolution of 640 x 200 pixels. The CGA card has two modes of operation: alphanumeric (A/N) and all points addressable (APA).In both modes, the basic character set is formed with a resolution of 8 x 8pixels. The CGA card displays either 40 or 80columns with 25 lines of text. In the A/N mode, the CGA card can display up to 16 colors. The all points addressable mode of operation can address each pixel individually. The CGA APA mode supports two resolutions on the screen: medium and high. The medium resolution is capable of addressing320 x 200 pixels with 4 colors. The high resolution is horizontal and vertical timing signals. Composite monitors can be either monochrome or color.RGB (red, green, blue) monitors are color monitors that use a separate input for each color. They have greater resolution than the composite videomonitors.EGA (Enhanced Graphics Adapter) and V G A(Video Graphics Array) monitors are RGB monitors that have even greater resolution. Both EGA and VGA monitors display sharper characters and graphics than does the RGB monitor. EGA monitors can display 43 lines of text instead of the standard 25lines of the RGB monitor. VGA monitors can display up to 50 lines of text.VGA monitors are designed to use analog signals rather than digital signals to drive the CRT guns. Digital signals limit the maximum number of colors that can be displayed to 16. By using variable(analog) signals to drive the CRT guns, current video adapters and monitors are capable of displaying over256,000 colors. The super VGA and XGA monitors also use analog signals. If you are upgrading your monitor, be sure that the display adapter is compatible with the new monitor. Also, there are multisync monitors that can be used with a variety of video cards. These monitors detect the rate that data is being received and adjust their scan rates to match the input. As you can see, the type of monitor you have must be compatible with the type of video card in the computer. You can literally burn up a monitor by plugging it into the wrong type of video card. Video monitors require very little preventive maintenance. They should be cleaned periodically to remove any dust that has collected on the components. Repair of a failed monitor is difficult because the monitor diagrams are hard to obtain from the manufacturer. Also, the price of the repair parts often exceeds the cost of a new monitor.
Advantages:
More room to run applications in, less scrolling side to side and up and down in your windows, more colors (this isn't necessarily true, but it is a closely related topic, and I'll address this issue below), more colors means nicer looking pictures (ever notice that annoying color banding (called dithering) in most of the pictures you look at), A much less cluttered appearance (unless you're one of those people who upon getting more space, feels the need to fill it up).
Disadvantages:
With higher resolutions and colors, there is a performance hit (speed), which could be big or small depending on your hardware and the resolution you set up (generally it's a very small performance hit). This is due to the fact that there is much more information to deal with as well as more pixels to update on-screen (I'll get to this below), The higher you set your resolution, the smaller your icons and text, and your refresh rate drops (I'll get to this too). Solid-state Display: Solid-state refers to electronic components, devices, and systems based entirely on the semiconductor . The expression was especially prevalent in the late 1950s and early 1960s, during the transition from vacuum tube technology to the semiconductor diode and transistor. More recently, the integrated circuit ( IC ), the light-emitting diode ( LED ), and the liquid-crystal display ( LCD ) have evolved as further examples of solid-state devices.
In a solid-state component, the current is confined to solid elements and compounds engineered specifically to switch and amplify it. Current flows in two forms: as negatively charged electrons, and as positively charged electron deficiencies called holes. In some semiconductors, the current consists mostly of electrons; in other semiconductors, it consists mostly of holes. Both the electron and the hole are called charge carriers.
An example of a non-solid-state component is a cathode-ray tube ( CRT ). In this device, electrons flow freely through a vacuum from an electron gun, through deflecting and focusing fields, and finally to a phosphorescent screen.
Unit-6 What is a Printer? A printer is an electromechanical device which converts the text and graphical documents from electronic form to the physical form. Generally they are the external peripheral devices which are connected with the computers or laptops through a cable or wirelessly to receive input data and print them on the papers. A wide range of printers are available with a variety of features ranging from printing black and white text documents to high quality colored graphic images.
Fig. 1: A Figure Showing Printer as an Electromechanical Device Converting Text into Graphical Content
Quality of printers is identified by its features like color quality, speed of printing, resolution etc. Modern printers come with multipurpose functions i.e. they are combination of printer, scanner, photocopier, fax, etc. To serve different needs there are variety of printers available that works on different types of technologies.
Types of Printers Since the invention of the printing technology, a variety of technologies have been employed in computer printers. Broadly printers are categorized as impact and non impact printers. Impact printers are the type of printers in which a key strikes the paper to make a letter. The examples of Impact printers are Daisy wheel and Dot matrix printers. While non-impact printers do not operate by striking a head against a ribbon. Inkjet printers and laser printers are the non-impact printers. The most popular printers are described.
1. Daisy Wheel Printers Daisy wheel printers print only characters and symbols and cannot print graphics. They are generally slow with a printing speed of about 10 to 75 characters per second. By 1980 daisy wheel printers were the dominant printers for quality printing but since the prices of laser and inkjet printers have declined and quality of dot matrix printers has been improved, the daisy wheel printers are now obsolete.
Fig. 2: An Image Showing Working of Daisy Wheel Printers for Printing Characters and Symbols Working of daisy wheel printers is very similar to typewriters. A circular printing element (known as daisy wheel, shown in the below image) is the heart of these printers that contains all text, numeric characters and symbols mould on each petal on the circumference of the circle. The printing element rotates rapidly with the help of a servo motor and pauses to allow the printing hammer to strike the character against the paper.
Fig. 3: An Image Representing Daisy Wheel, a Circular Printing Element Allowing Printing Hammer to Print Characters Against Paper Dot Matrix Printers
2. Dot Matrix Printers It is a popular computer printer that prints text and graphics on the paper by using tiny dots to form the desired shapes. It uses an array of metal pins known as printhead to strike an inked printer ribbon and produce dots on the paper. These combinations of dots form the desired shape on the paper. Generally they print with a speed of 50 to 500 characters per second as per the quality of the printing is desired. The quality of print is determined by the number of pins used (varying from 9 to 24).
Fig. 4: An Image Representing Dot Matrix Printers Printing Text and Graphics Using Tiny Dots in the Desired Shape The key component in the dot matrix printer is the ‘printhead’ which is about one inch long and contains a number of tiny pins aligned in a column varying from 9 to 24. The printhead is driven by several hammers which force each pin to make contact with the paper at the certain time. These hammers are pulled by small electromagnet (also called solenoids) which is energized at a specific time depending on the character to be printed. The timings of the signals sent to the solenoids are programmed in the printer for each character.
Fig. 5 : A Figure Illustrating Printheads Driven by Several Print Hammers Through Solenoids to Print Text
The printer receives the data from the computer and translates it to identify which character is to be printed and the print head runs back and forth, or in an up and down motion, on the page and prints the dots on the paper.
Inkjet Printers
3. Inkjet printers Inkjet printers are most popular printers for home and small scale offices as they have a reasonable cost and a good quality
Fig. 6: A Representational Image of Inkjet Printers to Produce Full Colored Hard Copies of printing as well. A typical inkjet printer can print with a resolution of more than 300 dpi and some good quality inkjet printers are able to produce full colored hard copies at 600 dpi. An inkjet printer is made of the following parts: · Printhead – It is the heart of the printer which holds a series a nozzles which sprays the ink drops over the paper. · Ink cartridge – It is the part that contains the ink for printing. Generally monochrome (black & white) printers contain a black colored ink cartridges and a color printer contains two cartridges – one with black ink and other with primary colors (cyan, magenta and yellow).
Stepper motor – It is housed in the printer to move the printerhead and ink cartridges back and forth across the paper. . Stabilizer bar – A stabilizer bar is used in printer to ensure the movement of printhead is précised and controlled over the paper. . Belt – A belt is used to attach the printhead with the stepper motor. . Paper Tray – It is the place where papers are placed to be printed. . Rollers – Printers have a set of rollers that helps to pull paper from the tray for printing purpose. . Paper tray stepper motor- another stepper motor is used to rotate the rollers in order to pull the paper in the printer. . Control Circuitry – The control circuit takes the input from the computer and by decoding the input controls all mechanical operation of the printer.
Similar to other printers, inkjet printers have a ‘printhead’ as a key element. The printhead has many tiny nozzles also called as jets. When the printer receives the command to print something, the printhead starts spraying ink over the paper to form the characters and images. There are mainly two technologies that are used to spray the ink by nozzles. These are: · Thermal Bubble – This technology is also known as bubble jet is used by various manufacturers like Canon and Hewlett Packard. When printer receives commands to print something, the current flows through a set of tiny resistors and they produce heat. This heat in turn vaporizes the ink to create a bubble. As the bubble expands, some of the ink moves out of the nozzle and gets deposited over the paper. Then the bubble collapses and due to the vacuum it pulls more ink from ink cartridge. There are generally 300 to 600 nozzles in a thermal printer head which can spray the ink simultaneously. · Piezoelectric – In the piezoelectric technology, a piezo crystal is situated at the end of the ink reservoir of a nozzle. When printer receives the command to print, an electric charge is applied to the crystal which in turn starts vibrating and a small amount of ink is pushed out of the nozzle. When the vibration stops the nozzle pulls some more ink from the cartridge to replace the ink sprayed out. This technology is patented by Seiko Epson Corporation.
An inkjet printer can print 100 to several hundred papers depending on the nature of the hard copy before the ink cartridge need to be replaced.
Laser Printers
4. Laser Printers Laser printers are the most popular printers that are mainly used for large scale qualitative printing. They are among the most popularly used fastest printers available in the market. A laser printer uses a slight different approach for printing. It does not use ink like inkjet printers, instead it uses a very fine powder known as ‘Toner’. Componetns of a laser printer is shown in the following image:
The control circuitry is the part of the printer that talks with the computer and receives the printing data. A Raster Image Processor (RIP) converts the text and images in to a virtual matrix of dots. The photoconducting drum which is the key component of the laser printer has a special coating which receives the positive and negative charge from a charging roller. A rapidly switching laser beam scans the charged drum line by line. When the beam flashes on, it reverses the charge of tiny spots on the drum, respecting to the dots that are to be printed black. As soon the laser scans a line, a stepper motor moves the drum in order to scan the next line by the laser.
A developer roller plays the vital role to paste the tonner on the paper. It is coated with charged tonner particles. As the drum touches the developer roller, the charged tonner particles cling to the discharged areas of the drum, reproducing your images and text reversely. Meanwhile a paper is drawn from the paper tray with help of a belt. As the paper passes through a charging wire it applies a charge on it opposite to the toner’s charge. When the paper meets the drum, due to the opposite charge between the paper and toner particles, the toner particles are transferred to the paper. A cleaning blade then cleans the drum and the whole process runs smoothly continuously. Finally paper passes through the fuser which is a heat and presser roller, melts the toner and fixes on the paper perfectly. Monochrome v/s Color
Monochrome v/s Color Printers Color printers work on the same concept of monochrome printers. They use four color toners (ink cartridges in case of inkjet printers) instead of one black colored toner in the black and white printers. Typically the colors are –Cyan, Magenta, Yellow and Black that are used to print in full color. There are four different drums and each drum is associated with the separate color toner. When printer receives the printing data, the paper is charged corresponding to the different color drums. The paper passes through each drum and the corresponding color toner particles gets stuck on the paper. As the paper passes through all four drums, the desired colored shape gets printed on the paper. Since the paper passes through four drums, color printers are four times slower than the monochrome printers and several times expensive.
The below video shows how exactly a color laser printer works:
Special Printers
5. Some special types of printers Despite these printers there are also some function specific printers these are designed for special purposes. Photo Printer – These inkjet printers are color printers that produce photo lab quality pictures on photo papers. Although they can also be used to print documents but they are specially designed for printing the photo. They have a large number of nozzles that can print very fine droplets to enhance the image quality. They can print a 4 x 6 inch photos directly from the digital cameras without need of a computer.
Fig. 10: A Representational Image of Photo Inkjet Printers Producing Photo Lab Quality Pictures on Photo Papers
Dye Sublimation Printers – These are latest innovative printers that are specially designed for high quality photo printing. They magnetize the ink over a charged paper to produce a very high quality picture. These printers are suitable to photo hobbyists but are a quite expensive.
Fig. 11: A Representational Image of Dye Sublimation Printers Designed Especially for High-Quality Printing Portable Printers - They are small light weight inkjet or thermal printers specially designed for the users to carry out with the laptops while travelling. Generally these printers have a lower quality for image printing and higher cost because of its compact design.
Fig. 12: A Representational Image of Portable Thermal or Inkjet Printers Ideal to Carry with Laptop Multifunction Printers – Also known as all in one printers are the combination of various functionalities like printer, scanner, photo copier, fax, etc.
Fig. 13: A Representational Image of Multifunction Printer Equipped with Scanner, Fax, Photo Copier, Printer, and etc.
Printer Mechanisms Information
Printer mechanisms are used in kiosks, lottery machines, ticketing machines, and cash registers. They include thermal, laser, and dot matrix printing technology. Printer mechanisms can be customized to handle different paper widths and paper ply. Products that are suitable for laser printing may provide additional features. Types
Printer mechanisms for cash registers, kiosks, automated teller machines, lottery machines, and other ticketing machines are typically small, compact units that take a spool or roll of paper that is printed per transaction, fed through an output slot, and automatically cut. These printer mechanisms are used for all kinds of receipts and records of self-service or automated transactions.
A cash register printer may use an ink jet, a dot matrix, or a thermal printer mechanism for producing receipts and coupons. A dot matrix printer uses a series of pins striking an ink ribbon to produce letters and images.
An inkjet printer transfers small, precisely placed droplets of ink on the page.
Thermal printer mechanisms use heat to transfer an impression on the paper. Thermal printers are high-speed devices and can also print logos or coupons in color. A lottery machine or other ticketing machine typically uses a thermal printer mechanism. Applications
Laser printer mechanisms are used in kiosks and self-service applications because of their high- speed delivery and print quality. Since a kiosk laser printer is capable of producing printouts in color, it is used to print more elaborate, formatted receipts and high-quality color copies. Laser printers are usually more expensive to operate and typically require more maintenance to replace toner cartridges. Laser printers may also have a larger footprint than a compact thermal printer or dot matrix printer.
You probably know that two most common types of printers for office and home use inkjet and laser. Though still might come across old matrix printers that are mostly used in banks.
Both ink and laser printers have their advantages and disadvantages.
Laser Printer
Laser printers include not only laser but also contain rotating cylinder coated with photosensitive electrically charged material and series of mirrors. When you are sending a document to a laser printer, laser light is reflected by the mirrors on to the cylinder which neutralizes electric charges in specific areas.
Thanks to the rotation of both cylinder and the mirrors, as well as the lasers are turning on and off at precisely correct moments the areas hit by the laser correspond to the actual print. So when the toner particles hit the cylinder they only stick to the areas exposed to the laser light, because the toner itself has an electrical charge too.
Then a sheet of paper is pressed against the cylinder and the toner is transferred through the paper using heat which fuses a toner to it. That is why pages right from the laser printer are always warm.Due to the precision of the laser these kinds of printers are great for producing crisp and clear text.
Inkjet printer
The other printer type – the inkjet printer, which uses a very different technology. This type of the printer uses liquid ink instead of solid toner particles.
In consumer models, inside of the very expensive cartridges. ink is heated with the electrical charge to vaporize an extremely small amount of ink and form a bubble on the nozzle. The bubble then collapses and the pressure difference pulls a droplet of ink out of the cartridge and on the paper.
Because the internal procedures of the inkjet printer are more simple than the ones of laser printers, they intend to be much cheaper. It is fact that inkjet cannot print as quickly as laser printers, however they can give much better print quality of the photos. So this technology will be the right choice for those who are looking to print their images from DSLR or phone at home.
On the other hand, lots of inkjet printer owners were disappointed by their printer’s reliability. This is partially caused by extra small moving parts can break. The small nozzles that were mentioned before can clog easily.
Another confusing thing about the inkjet printers is the business model of their manufacturers. The printers themselves are frequently sold for the price that is lower than their cost. That is why the ink usually refills cost a lot. Some manufactures program microchips inside of the cartridges to request ink refill even when the cartridge is not empty.
But the things are getting changed slowly. You can find alternative systems that can be integrated to your printer instead of the cartridges.
Printer Controller:
In a world where our devices are becoming more mobile and less dependent on a direct connection to a PC, why should you disc printer be any different. Previously, every printer that can print on optical discs required a direct connection to a computer to transfer the image file of the artwork. This was typically done through a USB capable and limited ones effort to allow their dupe and print operation to be more mobile. Vinpower has severed those restrictions with its new mobile standalone printer controller VPD-PRT. The new VPD-PRT can work with up to two printers allowing the artwork and operation functions to be controlled through a compact lightweight device which is extremely portable and easy to use.
Even if you’re not looking to use your printer outside of your business or home, why tie up your computer or need to purchase multiple computers just to operate your disc printer, when you can save money and time using Vinpower’s VPD-PRT. So when you’re ready to cut the ties from your printer and save money at the same time, the VPD-PRT is your best solution.
Before a laser printer can do anything else, it needs to receive the page data and figure out how it's going to put everything on the paper. This is the job of the printer controller.
The printer controller is the laser printer's main onboard computer. It talks to the host computer (for example, your PC) through a communications port, such as a parallel port or USB port. At the start of the printing job, the laser printer establishes with the host computer how they will exchange data. The controller may have to start and stop the host computer periodically to process the information it has received.
In an office, a laser printer will probably be connected to several separate host computers, so multiple users can print documents from their machine. The controller handles each one separately, but may be carrying on many "conversations" concurrently. This ability to handle several jobs at once is one of the reasons why laser printers are so popular.
Key Features:
1. Work standalone with printers. Do not need to use PC. Excellent when having many printers. It saves a lot of space for set up PCs. Easy to carry around. 2. Supports many key optical disc printer brands, including Primera / Epson / Canon / HP / TEAC
• Primera Bravo 4100, Bravo se • Epson A50,T50,P50,R290,L800 • Canon iPx4970 • HP FlashJet, Puma • TEAC P55
3. Support printing two different printers with different printing jobs concurrently. 4. Support Vinpower Pandora AutoPrinter Series. 5. Support PRN files in the USB device as the image sources. 6. Support different file format of the USB device
Definition - What does Centronics Interface mean?
The Centronics interface is a standard input/output (I/O) interface designed in the 1970s for connecting printers and other devices. It was developed by the Centronics printer company which is now defunct. The Centronics interface, also known as a Parallel Port, became the standard means of connecting printers to personal computers for decades.
The technology that the Centronics interface developed into included a number of incarnations of the Parallel interface including the ECP (Entended Capabilities Parallel) and EPP (Enhanced Parallel Port) versions. The technology required a 25 way connector of which up to 17 wires were used in the specification and bi-directional communications became possible in the enhanced versions like ECP and EPP.Today, the Centronics interface has been largely replaced by the universal serial bus (USB). For the most part, many manufactures have entirely omitted the parallel interface. However, a USB-to-parallel port adapter is available for PCs without a parallel port. These can be used for parallel printers and other peripheral devices that have a parallel interface.
The Centronics interface is also known as a the Centronics port, Centronics parallel interface, parallel port or printer port.
The first parallel port for printers was the Centronics Model 101, which transmitted data eight bits at a time. Later, parallel ports became bidirectional and were used for printers and input devices.
The original Centronics Model 101 was cost effective and very advanced for its time. It had a print speed of 125 characters per second and weighed 155 pounds.The interface used a Centronics parallel port, but an RS-232 serial port was optional. In the original Centronics interface, data flowed in one direction only but used eight parallel data lines which was a technological advance of the day. Serial communications were sent down in sequence so in theory the parallel port was eight times faster, although in reality the speed was about triple at most.
When the IEEE 1284 standard was introduced in 1994, the logic voltages, length of cables and the interface were all standardized. The IEEE 1284's five standard were specified to support data transfer in the forward direction, backward direction, or bi-directionally. The five modes of operation are:
1. Extended capability port (ECP) mode 2. Enhanced parallel port (EPP) mode 3. Byte mode 4. Nibble mode 5. Compatibility (standard parallel port or SPP) mode
How to Connect a Printer to Your Computer
This wikiHow teaches you how to connect a printer wired or wireless printer to your Windows or Mac computer. Once connected, you can also share the printer on your home network, allowing other computers in your house to print from it even though they aren't directly connected.
Method 1
Connecting a Wired Printer on Windows
1.
1
Set your printer near your computer. Make sure that it is close enough that the cable can reach your computer without tension.
2.
2
Turn on your printer. Press your printer's power button; it will likely have a
icon on or next to it.
o Your printer must be plugged into a power source.
3 With you computer turned on and unlocked, plug the printer into your computer using a USB cable.
o In some cases, simply plugging your printer into your computer in this way will automatically setup and properly install the printer, making it ready to use.
4
Open Start
. Click the Windows logo in the bottom-left corner of the screen.
5
Click Settings
. It's in the lower-left side of the Start window.
6
Click Devices. This option is near the top of the Settings window.
7 Click Printers & scanners. It's a tab on the left side of the window.
8
Click Add a printer or scanner. This button is at the top of the page.
9 Click your printer's name and click Add device. This will typically be a combination of the printer's manufacturer (e.g., "HP"), the printer's model name, and the model number.
o If you don't see your printer's name here, click the The printer that I want isn't listed link below the Add a printer or scanner button and follow the on-screen instructions.
10
Follow the on-screen instructions. Depending on your printer, you may need to customize your settings before the printer is ready; once you're done, the printer will be available for use.
o If prompted, insert the CD that came with your printer into your computer's disc slot. o If you bought your printer second-hand and didn't come with a CD, you can usually download the same software from the manufacturer's website.
UNIT-7
A network is defined as a group of two or more computer systems linked together. There are many types of computer networks, including the following:
local-area networks (LANs): The computers are geographically close together (that is, in the same building).
wide-area networks (WANs): The computers are farther apart and are connected by telephone lines or radio waves.
campus-area networks (CANs): The computers are within a limited geographic area, such as a campus or military base.
metropolitan-area networks MANs): A data network designed for a town or city.
home-area networks (HANs): A network contained within a user's home that connects a person's digital devices.
Network Characteristics
In addition to these types, the following characteristics are also used to categorize different types of networks:
topology : The geometric arrangement of a computer system. Common topologies include a bus, star, and ring. See the Network topology diagrams in the Quick Reference section of Webopedia.
protocol : The protocol defines a common set of rules and signals that computers on the network use to communicate. One of the most popular protocols for LANs is called Ethernet. Another popular LAN protocol for PCs is the IBM token-ring network .
architecture : Networks can be broadly classified as using either a peer-to-peer or client/server architecture.
Computers on a network are sometimes called nodes. Computers and devices that allocate resources for a network are called servers.
Computer Networking Devices Explained with Function
This tutorial explains the functions of the most common and the essential networking devices (such as Hub, Switch, Router, Bridge, Modem, NIC, Proxy and Gateway) in detail with examples.
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Network Interface Card (NIC)
In the list of the networking devices, NIC stands on the first place. Without this device, networking cannot be done. This is also known as network adapter card, Ethernet Card and LAN card. NIC allows a networking device to communicate with the other networking device.
NIC converts the data packets between two different data transmission technologies. A PC uses parallel data transmission technology to transmit the data between its internal parts while the media that provides connectivity between different PCs uses serial data transmission technology.
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A NIC converts parallel data stream into the serial data stream and the serial data stream into the parallel data stream.
Typically all modern PCs have the integrated NICs in the motherboards. If additional NICs are required, they are also available as add-on devices separately.
For desktop or server system, they are available in the adapter form which can be plugged into the available slots of the motherboard. For laptop or other small size devices, they are available in the PCMCIA (Personal Computer Memory Card International Association) card form which can be inserted into the PCMCIA slot. Types of NICs
There are two types of NICs.
Media Specific: - LAN card are used according to the media type. Different types of the NICs are used to connect the different types of media. To connect a specific media type, we must have to use a NIC which is particularly made for that type of media.
Network Design Specific: - A specific network design needs a specific LAN card. For example FDDI, Token Ring and Ethernet have their own distinctive type of NIC cards. They cannot use other types of NIC cards.
Following figure illustrates some common types of NICs.
Hub
Hub is a centralized device that connects multiple devices in a single LAN network. When Hub receives the data signals from a connected device on any of its port, except that port, it forwards those signals to all other connected devices from the remaining ports. Usually, Hub has one or more uplink ports that are used to connect it with another Hub.
A hub is basically a multiport repeater. A hub connects multiple wires coming from different branches, for example, the connector in star topology which connects different stations. Hubs cannot filter data, so data packets are sent to all connected devices. In other words, collision domain of all hosts connected through Hub remains one. Also, they do not have intelligence to find out best path for data packets which leads to inefficiencies and wastage.
Types of Hub
Active Hub :- These are the hubs which have their own power supply and can clean , boost and relay the signal along the network. It serves both as a repeater as well as wiring center. These are used to extend maximum distance between nodes. It also works same as the passive Hub works. But before forwarding the data signals, it amplifies them. Due to this added feature, the active Hub is also known as the repeater.
Passive Hub :- These are the hubs which collect wiring from nodes and power supply from active hub. These hubs relay signals onto the network without cleaning and boosting them and can’t be used to extend distance between nodes. It forwards data signals in the same format in which it receives them. It does not change the data signal in any manner.
MAU and Patch panel
MAU and Patch Panel look like the Hub, but they are different. MAU (Multi Access Unit) is the sibling of Hub for the token ring network. Differences between Hub and MAU are the following: -
Hub is used for the Ethernet Network while the MAU is used for the Token ring network. Hub creates logically star topology while MAU creates logically ring topology.
Patch panel is used to organize the UTP cables systematically. It doesn't interfere in the data signals.
Bridge
Bridge is used to divide a large network into smaller segments. Basic functions of the Bridge are the following: -
Breaking a large network into smaller segments. Connecting different media types. Such as connects UTP with the fiber optic. Connecting different network architectures. Such as connects Ethernet with the Token ring.
A Bridge can connect two different types of media or network architecture, but it cannot connect two different types of network layer protocol such as TCP/IP or IPX. Bridge requires the same network layer protocol in all segments. A bridge operates at data link layer. A bridge is a repeater, with add on functionality of filtering content by reading the MAC addresses of source and destination. It is also used for interconnecting two LANs working on the same protocol. It has a single input and single output port, thus making it a 2 port device.
Types of Bridges
Transparent Bridges :- These are the bridge in which the stations are completely unaware of the bridge’s existence i.e. whether or not a bridge is added or deleted from the network , reconfiguration of the stations is unnecessary. These bridges makes use of two processes i.e. bridge forwarding and bridge learning. Source Routing Bridges :- In these bridges, routing operation is performed by source station and the frame specifies which route to follow. The hot can discover frame by sending a specical frame called discovery frame, which spreads through the entire network using all possible paths to destination.
There are three types of Bridge:-
Local Bridge: - This Bridge connects two LAN segments directly. In Ethernet Implementation, it is known as the Transparent Bridge. In Token Ring network, it is called the Source-Routed Bridge.
Remote Bridge: - This Bridge connects with another Bridge over the WAN link.
Wireless Bridge: - This Bridge connects with another Bridge without using wires. It uses radio signals for the connectivity.
In OSI Layers /TCP-IP networking models, the functionalities of the Bridges are defined in the physical layer and data link layer. Just like Hubs, Bridge no longer used in the computer network. Bridges have been replaced by the Switches.
Switch
Just like Hub and Bridge, Switch is also used to connect the multiple devices together in a LAN segment. Basically, a Switch is the upgraded version of the Bridge. Besides providing all the functionalities of Bridge, it also offers several additional features.
A switch is a multi port bridge with a buffer and a design that can boost its efficiency(large number of ports imply less traffic) and performance. Switch is data link layer device. Switch can perform error checking before forwarding data, that makes it very efficient as it does not forward packets that have errors and forward good packets selectively to correct port only. In other words, switch divides collision domain of hosts, but broadcast domain remains same.
The biggest advantage of Switch is that, it makes switching decisions in hardware by using application specific integrated circuits (ASICs).
Unlike the generic processors that we use in our PC, ASICs are the specialized processors built only to perform very few particular tasks. Usually, the ASICs in the Switches have single task and that is the switching the frames as fast as possible.
An ASIC occupied switch performs this task blazingly fast. For example, an entry level Catalyst Switch 2960 can process 2.7 million frames per second.
Modem
In simple language, a Modem is the device that is used to connect with the Internet. Technically, it is the device that enables the digital data to be transmitted over the telecommunication lines.
A Telco company uses entirely different data transmission technology from the technology that a PC uses for the data transmission. A modem understands both technologies. It changes the technology that a PC uses, in the technology which Telco Company understands. It enables communication between the PC (Known as the DTE device) and the Telecom company' office (Known as the DCE device).
Following figure shows some common types of the Modem.
Gateway
A gateway, as the name suggests, is a passage to connect two networks together that may work upon different networking models. They basically works as the messenger agents that take data from one system, interpret it, and transfer it to another system. Gateways are also called protocol converters and can operate at any network layer. Gateways are generally more complex than switch or router.Gateway is used to forward the packets which are generated from the local host or network and but intended for the remote network. If a data packet does not find its destination address in the local network then it takes the help of the gateway device to find the destination address in the remote network. A gateway device knows the path of the remote destination address. If require, it also changes the encapsulation of the packet so it can travel through the other networks to get its destination address.
Examples of the Gateway
Email Gateway: - Translates SMTP e-mail in standard X.400 format before forwarding.
GSNW Gateway: - Allows Windows clients to access resources from the NetWare server.
PAD Gateway: - Provides connectivity between LAN network and X.25 network.
Router
The router connects the different network segments. It switches the data packets between those networks which are either located in the different logical segments or built with the different network layer protocols.
When a router receives a data packet on any of its interface, it checks the destination address of that packet and based on that destination address, it forwards that data packet from the interface which is connected with the destination address.
To forward a data packet to its destination, router keeps the records of connected networks. These records are maintained in a database table known as the routing table. Routing table can be built statically or dynamically. A router is a device like a switch that routes data packets based on their IP addresses. Router is mainly a Network Layer device. Routers normally connect LANs and WANs together and have a dynamically updating routing table based on which they make decisions on routing the data packets. Router divide broadcast domains of hosts connected through it.
Basically routers are used: -
To connect different network segments. To connect different network protocols such as IP and IPX. To connect several smaller networks into a large network (known as the Internetwork) To break a large network into smaller networks (Known as the Subnets. Usually created to improve the performance or manageability.) To connect two different media types such as UTP and Fiber optical. To connect two different network architectures such as Token Ring and Ethernet. To connect LAN network with Telco company’ office (Known as the DTE device). To access DSL services (known as the DSL Router).
Proxy
Proxy is used to hide the internal network from external world. It can be a dedicate device or can be an application software. Once it is configured, all communication goes through it. Since external devices cannot access the internal devices directly, they cannot tamper with the internal devices.
Transceiver
Transceiver is a small device that has the capability of receiving and sending both types of signals; analog and digital. Usually, it is inbuilt in network interface card. But, it is also available as an individual device. It detects the type of signal from the network wire and converts the passing signal accordingly.
For example, a transceiver is attached with a device that transmits signal in digital form. Now suppose, this device is connected with the network wire that uses analog form for data transmission. In this case, transceiver converts digital signals in the analog signals before placing them in the network wire
What is LAN (Local Area Network) : what is lan: It actually stands for local area network. A network is a group of computers and other devices connected together so they can pass information back and forth. The local area network (LAN) is a network which is designed to operate over a small physical area such as an office, factory or a group of buildings. LANs are very widely used in a variety of applications.
Lan Definition
The personal computers and workstations in the offices are interconnected via LAN to share resources. The resources to be shared can be hardware like a printer or softwares or data. A LAN is a form of local (limited-distance), shared packet network for computer communications. In LAN all the machines are connected to a single cable. The data rates for LAN range from 4 to 16 Mbps with the maximum of 100 Mbps. The term LAN can also refer just to the hardware and software that allows you to connect all the devices together. In this sense, Local Talk is one kind of LAN, Ethernet is another. (AppleTalk is the protocol for Local Talk.)
The components used by LANs can be divided into cabling standards, hardware, and protocols. Various LAN protocols are Ethernet, Token Ring: TCP/IP, 5MB, NetBIOS and NetBeui, IPX/SPX, Fiber Distributed Data Interchange (FDDI) and Asynchronous Transfer Mode (ATM).
Types of lan
Ethernet is the most common type of LAN. Different Lan can be differentiated on the behalf of following characteristics.
Topology: The topology is the geometric arrangement of a network elements. For example, Network devices can be interconnected in a ring topology or in a bus topology or linear bus.
Protocols: It is a guidelines for communicating data between two devices. The protocols also determine type of error and data compression. Media: The cable used in Lan to connect devices are twisted-pair wire, coaxial cables, or fiber optic.
Wan vs Lan
LAN's are also distinguished from MAN's and WAN's based on the transmission media they use and topology. In general a given LAN will use only one type of transmission medium. The most common topologies used are bus, ring and star. Two or more interconnects different smaller networks are called a wide-area network (WAN).The difference between a LAN and WAN is that the WAN spans a relatively large geographical distance such as across cities, states, or countries.
Example of Lan Topologies
Various topologies are possible for the broadcast LANs such as bus topology or ring topology.
Bus Topology
• Bus topology is shown in Fig. In this topology at any instant only one computer acts as master and it is allowed to transmit (broadcast). The others are supposed to listen.
• If two or more machines want to transmit simultaneously then an arbitration mechanism has to be used for resolving the conflict.
• It is possible to have a centralized or distributed type arbitration mechanism.
• The most popular example of bus topology is Ethernet (IEEE 802.3). It has a decentralized control and it operates at 10 or 100 Mbps.
• Computers on Ethernet can transmit whenever they want. If collision of their packets takes place, then they wait for a random time and retransmit their packets.
Ring Topology
• This is another broadcast topology.
• In a ring each bit propagates around on its own without waiting for the rest of the packet to which it belongs.
• Since it is a broadcast system, some rules are essential for arbitrating the simultaneous access to the ring.
• An example of ring based LAN is IEEE 802.5 (IBM token ring) operating at 4 and 16 Mbps.
Static and dynamic broadcast networks:
• The broadcast networks are further classified into two types namely,
1. Static networks and
2. Dynamic networks. • This classification is based on how the channel is allocated.
• In static allocation, each machine is allowed to broadcast only in its allotted time slot.
• But static allocation wastes the channel capacity when a machine does not want to transmit in its allotted time slot.
• Hence most of the systems try to allocate the channel dynamically i.e. on demand.
LAN Applications and Benefits
LANs are used almost exclusively for data communications over relatively short distances such as within an office, office building or campus environment. LANs allow multiple workstations to share access to multiple host computers, other workstations, printers and other peripherals, and connections to other networks. LANs are also being utilized for imaging applications, as well. They are also being used for video and voice communications, although currently on a very limited basis.
LAN applications include communications between the workstation and host computers, other workstations, and servers. The servers may allow sharing of resources. Resources could be information, data files, e-mail, voice mail, software, hardware (hard disk, printer, fax, etc.) and other networks.
LAN benefits include the fact that a high-speed transmission system can be shared among multiple devices in support of large number of active terminals and a large number of active applications in the form of a multi-user, multi-tasking computer network. LAN-connected workstations realize the benefit of decentralized access to very substantial centralized processors, perhaps in the form of mainframe host computer and storage capabilities (information repositories). Additionally, current technology allows multiple LANs to be inter- networked through the use of LAN switches, routers and the like.
WAN:
A wide-area network (WAN) is any telecommunications network or computer network that extends over a large geographical distance/place. Wide-area networks are often established with leased telecommunication circuits.
Business, education and government entities use wide-area networks to relay data to staff, students, clients, buyers, and suppliers from various locations across the world. In essence, this mode of telecommunication allows a business to effectively carry out its daily function regardless of location. The Internet may be considered a WAN.
A wide area network (WAN) is a geographically distributed private telecommunications network that interconnects multiple local area networks (LANs). In an enterprise, a WAN may consist of connections to a company's headquarters, branch offices, colocation facilities, cloud services and other facilities. Typically, a router or other multifunction device is used to connect a LAN to a WAN. Enterprise WANs allow users to share access to applications, services and other centrally located resources. This eliminates the need to install the same application server, firewall or other resource in multiple locations, for example.
A virtual private network (VPN) facilitates connectivity between WAN sites. An IPsec VPN is more commonly used in continuously open site-to-site connections, such as those between branch offices and headquarters locations. An SSL VPN is often the preferred choice for enabling remote access for individual users because the data transmitted from users across the WAN is encrypted. Direct fiber optic links are also used to connect sites on a WAN – and they almost always offer greater performance, reliability and security than VPNs, but they are cost- prohibitive for most enterprises to procure and operate.
Types of WAN connections
WAN connections can include wired and wireless technologies. Wired WAN services can include multiprotocol label switching, T1s, Carrier Ethernet and commercial broadband internet links. Wireless WAN technologies can include cellular data networks like 4G LTE, as well as public Wi- Fi or satellite networks.
WANs over wired network connections remain the preferred medium for most enterprises, but wireless WAN technologies, based on the 4G LTE standard, are gaining traction.
WAN infrastructure may be privately owned or leased as a service from a third-party service provider, such as a telecommunications carrier, internet service provider, private IP network operator or cable company. The service itself may operate over a dedicated, private connection -- often backed by a service-level agreement -- or over a shared, public medium like the internet. Hybrid WANs employ a combination of private and public network services.
Software-defined WAN (SD-WAN) is designed to make hybrid WAN architectures easier for enterprises to deploy, operate and manage. Using a combination of virtualization, application- level policies and network overlays, on-site SD-WAN devices, software platforms or customer premises equipment (CPE) perform two functions:
1. They aggregate multiple public and private WAN links. 2. They automatically select the most optimal path for traffic, based on real-time conditions.
The latter function has historically required network managers to manually reconfigure their networks any time they wanted to shape the direction of traffic over multiple routes.
WAN optimization
Latency and bandwidth constraints often cause enterprise WANs to suffer from performance issues. WAN optimization appliances use a variety of techniques to counteract them, including deduplication, compression, protocol optimization, traffic shaping and local caching. SD-WAN CPE or platforms provide another level of application performance control through the use of lower-cost bandwidth connections, usually in the form of commercial internet services, along with traffic shaping and quality of service tools -- to increase reliability.
wireless LAN (WLAN or Wireless Local Area Network)
A wireless LAN (or WLAN, for wireless local area network, sometimes referred to as LAWN, for local area wireless network) is one in which a mobile user can connect to a local area network (LAN) through a wireless (radio) connection. The IEEE 802.11 group of standards specify the technologies for wireless LANs. 802.11 standards use the Ethernet protocol and CSMA/CA (carrier sense multiple access with collision avoidance) for path sharing and include an encryption method, the Wired Equivalent Privacy algorithm.
High-bandwidth allocation for wireless will make possible a relatively low-cost wiring of classrooms in the United States. A similar frequency allocation has been made in Europe. Hospitals and businesses are also expected to install wireless LAN systems where existing LANs are not already in place.
Stands for "Wireless Local Area Network." A WLAN, or wireless LAN, is a network that allows devices to connect and communicate wirelessly. Unlike a traditional wired LAN, in which devices communicate over Ethernet cables, devices on a WLAN communicate via Wi-Fi. While a WLAN may look different than a traditional LAN, it functions the same way. New devices are typically added and configured using DHCP. They can communicate with other devices on the network the same way they would on a wired network. The primary difference is how the data is transmitted. In a LAN, data is transmitted over physical cables in a series of Ethernet packets containing. In a WLAN, data is transmitted over the air using one of Wi-Fi 802.11 protocols.
As wireless devices have grown in popularity, so have WLANs. In fact, most routers sold are now wireless routers. A wireless router serves as a base station, providing wireless connections to any Wi-Fi-enabled devices within range of the router's wireless signal. This includes laptops, tablets, smartphones, and other wireless devices, such as smart appliances and smart home controllers. Wireless routers often connect to a cable modem or other Internet-connected device to provide Internet access to connected devices.
LANs and WLANs can be merged together using a bridge that connects the two networks. Many wireless routers also include Ethernet ports, providing connections for a limited number of wireless devices. In most cases, wireless routers act as a bridge, merging the Ethernet and Wi- Fi-connected devices into the same network. This allows wired and wireless devices to communicate with each other through a single router.
Advantages of WLANs
The most obvious advantage of a WLAN is that devices can connect wirelessly, eliminating the need for cables. This allows homes and businesses to create local networks without wiring the building with Ethernet. It also provides a way for small devices, such as smartphones and tablets, to connect to the network. WLANs are not limited by the number of physical ports on the router and therefore can support dozens or even hundreds of devices. The range of a WLAN can easily be extended by adding one or more repeaters. Finally, a WLAN can be easily upgraded by replacing routers with new versions — a much easier and cheaper solution than upgrading old Ethernet cables.
Disadvantages of WLANs
Wireless networks are naturally less secure than wired networks. Any wireless device can attempt to connect to a WLAN, so it is important to limit access to the network if security is a concern. This is typically done using wireless authentication such as WEP or WPA, which encrypts the communication. Additionally, wireless networks are more susceptible to interference from other signals or physical barriers, such as concrete walls. Since LANs offer the highest performance and security, they are still used for many corporate and government networks. How Wi-Fi Networks Works Wi-Fi networks have no physical wired connection between sender and receiver by using radio frequency (RF) technology -- a frequency within the electromagnetic spectrum associated with radio wave propagation. When an RF current is supplied to an antenna, an electromagnetic field is created that then is able to propagate through space.
The cornerstone of any wireless network is an access point (AP). The primary job of an access point is to broadcast a wireless signal that computers can detect and "tune" into. In order to connect to an access point and join a wireless network, computers and devices must be equipped with wireless network adapters. The Wi-Fi Alliance
The Wi-Fi Alliance, the organization that owns the Wi-Fi registered trademark term specifically defines Wi-Fi as any "wireless local area network (WLAN) products that are based on the Institute of Electrical and Electronics Engineers' (IEEE) 802.11 standards."
Initially, Wi-Fi was used in place of only the 2.4GHz 802.11b standard, however the Wi-Fi Alliance has expanded the generic use of the Wi-Fi term to include any type of network or WLAN product based on any of the 802.11 standards, including 802.11b, 802.11a, dual-band and so on, in an attempt to stop confusion about wireless LAN interoperability. Wi-Fi Support in Applications and Devices
Wi-Fi is supported by many applications and devices including video game consoles, home networks, PDAs, mobile phones, major operating systems, and other types of consumer electronics. Any products that are tested and approved as "Wi-Fi Certified" (a registered trademark) by the Wi-Fi Alliance are certified as interoperable with each other, even if they are from different manufacturers. For example, a user with a Wi-Fi Certified product can use any brand of access point with any other brand of client hardware that also is also "Wi-Fi Certified".
Products that pass this certification are required to carry an identifying seal on their packaging that states "Wi-Fi Certified" and indicates the radio frequency band used (2.5GHz for 802.11b, 802.11g, or 802.11n, and 5GHz for 802.11a).
What is a Router For?
A router is the first line of security from intrusion into a network. Enabling the highest level of security on the router is the best way to keep your computer system and information safe from attack.
Routers contain software called firmware that should be updated as released by the router manufacturer. Most routers connect to other network devices only via network cables and do not require drivers to operate in Windows or other operating systems. However, routers that connect to a computer via a USB or FireWire typically require drivers to operate properly.
Routers often act as the DHCP servers in small networks, issuing unique IP addresses.
Most routers are manufactured by companies like Linksys, 3Com, Belkin, D-Link, Motorola, TRENDnet, and Cisco, but there are many others.
How Routers Work
Routers connect a modem — like a fiber, cable, or DSL modem — to other devices to allow communication between those devices and the Internet. Most routers, even wireless routers, usually feature several network ports to connect numerous devices to the Internet simultaneously.
Typically, a router connects physically, via a network cable, to the modem via the 'Internet' or 'WAN' port and then physically, again via a network cable, to the network interface card in whatever wired network devices you may have. A wireless router can connect via various wireless standards to devices that also support the particular standard used.
The IP address assigned to the 'WAN' or 'Internet' connection is a public IP address. The IP address assigned to the 'LAN' or local network connection is a private IP address. The private IP addresses assigned to a router is usually the default gateway for the various devices on the network.
Wireless routers, and wired routers with multiple connections, also act as simple network switches allowing the devices to communicate with each other. For example, several computers connected to a router can be configured to share printers and files amongst themselves.
UNIT-8 Laptop:
A laptop computer (also shortened to just laptop; or called a notebook or notebook computer) is a small, portable personal computer (PC) with a "clamshell" form factor, typically having a thin LCD or LED computer screen mounted on the inside of the upper lid of the clamshell and an alphanumeric keyboard on the inside of the lower lid. The clamshell is opened up to use the computer. Laptops are folded shut for transportation, and thus are suitable for mobile use. Its name comes from lap, as it was deemed to be placed on a person's lap when being used. Although originally there was a distinction between laptops and notebooks (the former being bigger and heavier than the latter), as of 2014, there is often no longer any difference. Laptops are commonly used in a variety of settings, such as at work, in education, for playing games, Internet surfing, for personal multimedia, and general home computer use.
Laptops combine all the input/output components and capabilities of a desktop computer, including the display screen, small speakers, a keyboard, hard disk drive, optical disc drive, pointing devices (such as a touchpad or trackpad), a processor, and memory into a single unit. Most modern laptops feature integrated webcams and built-in microphones, while many also have touchscreens. Laptops can be powered either from an internal battery or by an external power supply from an AC adapter. Hardware specifications, such as the processor speed and memory capacity, significantly vary between different types, makes, models and price points. Hardware
Miniaturization: a comparison of a desktop computer motherboard (ATX form factor) to a motherboard from a 13" laptop (2008 unibody Macbook)
Inner view of a Sony VAIO laptop
A SODIMM memory module
The basic components of laptops function identically to their desktop counterparts. Traditionally they were miniaturized and adapted to mobile use, although desktop systems increasingly use the same smaller, lower-power parts which were originally developed for mobile use. The design restrictions on power, size, and cooling of laptops limit the maximum performance of laptop parts compared to that of desktop components, although that difference has increasingly narrowed.
Display
Internally, a display is an LCD panel which could be TFT backlit or LED backlit which talks to the laptop using the LVDS protocol, while externally, it can be a glossy screen or a matte screen. Most modern laptops feature a 13 inches (33 cm) or larger color active matrix display based on LED lighting with resolutions of 1280×800 (16:10) or 1366×768 (16:9) pixels and above. Models with LED-based lighting offer lesser power consumption and often increased brightness. Netbooks with a 10 inches (25 cm) or smaller screen typically use a resolution of 1024×600, while netbooks and subnotebooks with an 11.6 inches (29 cm) or 12 inches (30 cm) screen use standard notebook resolutions.
Central processing unit
A laptop's central processing unit (CPU) has advanced power-saving features and produces less heat than one intended purely for desktop use. Typically, laptop CPUs have two processor cores, although 4-core models are also available. For low price and mainstream performance, there is no longer a significant performance difference between laptop and desktop CPUs, but at the high end, the fastest 4-to-8-core desktop CPUs still substantially outperform the fastest 4-core laptop processors, at the expense of massively higher power consumption and heat generation; the fastest laptop processors top out at 56 watts of heat, while the fastest desktop processors top out at 150 watts.
Graphical processing unit
On most laptops a graphical processing unit (GPU) is integrated into the CPU to conserve power and space. This was introduced by Intel with the Core i-series of mobile processors in 2010, and similar accelerated processing unit (APU) processors by AMD later that year. Prior to that, lower-end machines tended to use graphics processors integrated into the system chipset, while higher end machines had a separate graphics processor. In the past, laptops lacking a separate graphics processor were limited in their utility for gaming and professional applications involving 3D graphics, but the capabilities of CPU-integrated graphics have converged with the low-end of dedicated graphics processors in the past few years.
Memory
Most laptops use SO-DIMM (small outline dual in-line memory module) memory modules, as they are about half the size of desktop DIMMs. They are sometimes accessible from the bottom of the laptop for ease of upgrading, or placed in locations not intended for user replacement. Most laptops have two memory slots, although some of the lowest-end models will have only one, and some high end models (usually mobile engineering workstations and a few high-end models intended for gaming) have four slots. Most mid-range laptops are factory equipped with 4–6 GB of RAM. Netbooks are commonly equipped with only 1–2 GB of RAM and are generally only expandable to 2 GB, if at all. Laptops may have memory soldered to the motherboard to conserve space, which allows the laptop to have a thinner chassis design. Soldered memory cannot be easily upgraded.
Internal storage
Traditionally, laptops had a hard disk drive (HDD) as a main non-volatile storage, but these proved inefficient for use in mobile devices due to high power consumption, heat production, and a presence of moving parts, which can cause damage to both the drive itself and the data stored when a laptop is unstable physically, e.g. during its use while transporting it or after its accidental drop. With the advent of flash memory technology, most mid- to high-end laptops opted for more compact, power efficient, and fast solid-state drives (SSD), which eliminated the hazard of drive and data corruption caused by a laptop's physical impacts.
Removable media drive
Optical disc drives capable of playing CD-ROMs, compact discs (CD), DVDs, and in some cases, Blu-ray Discs (BD), were nearly universal on full-sized models by the early 2010s. A disc drive remains fairly common in laptops with a screen wider than 15 inches (38 cm), although the trend towards thinner and lighter machines is gradually eliminating these drives and players; these drives are uncommon in compact laptops, such as subnotebooks and netbooks. Laptop optical drives tend to follow a standard form factor, and usually have a standard mSATA connector. It is often possible to replace an optical drive with a newer model. In certain laptop models there is a possibility to replace an optical drive with a second hard drive, using a caddy that fills the extra space the optical drive would have occupied.
Inputs
Closeup of a touchpad on an Acer laptop
Closeup of a TrackPoint cursor and UltraNav buttons on a ThinkPad laptop
An alphanumeric keyboard is used to enter text and data and make other commands (e.g., function keys). A touchpad (also called a trackpad), a pointing stick, or both, are used to control the position of the cursor on the screen, and an integrated keyboard is used for typing. An external keyboard and mouse may be connected using a USB port or wirelessly, via Bluetooth or similar technology. With the advent of ultrabooks and support of touch input on screens by 2010-era operating systems, such as Windows 8.1, multitouch touchscreen displays are used in many models. Some models have webcams and microphones, which can be used to communicate with other people with both moving images and sound, via Skype, Google Chat and similar software. Laptops typically have USB ports and a microphone jack, for use with an external mic. Some laptops have a card reader for reading digital camera SD cards.
Input/output (I/O) ports
On a typical laptop there are several USB ports, an external monitor port (VGA, DVI, HDMI or Mini DisplayPort), an audio in/out port (often in form of a single socket) is common. It is possible to connect up to three external displays to a 2014-era laptop via a single Mini DisplayPort, utilizing multi-stream transport technology. Apple, in a 2015 version of its MacBook, transitioned from a number of different I/O ports to a single USB-C port. This port can be used both for charging and connecting a variety of devices through the use of aftermarket adapters.
Expansion cards
In the past, a PC Card (formerly PCMCIA) or ExpressCard slot for expansion was often present on laptops to allow adding and removing functionality, even when the laptop is powered on; these are becoming increasingly rare since the introduction of USB 3.0. Some internal subsystems such as: Ethernet, Wi-Fi, or a wireless cellular modem can be implemented as replaceable internal expansion cards, usually accessible under an access cover on the bottom of the laptop.
Battery and power supply
Almost all laptops use smart batteries
A laptop's battery is charged using an external power supply which is plugged into a wall outlet. The power supply outputs a DC voltage typically in the range of 7.2—24 volts. The power supply is usually external and connected to the laptop through a DC connector cable. In most cases, it can charge the battery and power the laptop simultaneously. When the battery is fully charged, the laptop continues to run on power supplied by the external power supply, avoiding battery use. The battery charges in a shorter period of time if laptop is turned off or sleeping.
Cooling
Waste heat from operation is difficult to remove in the compact internal space of a laptop. Early laptops used heat sinks placed directly on the components to be cooled, but when these hot components are deep inside the device, a large space-wasting air duct is needed to exhaust the heat. Modern laptops instead rely on heat pipes to rapidly move waste heat towards the edges of the device, to allow for a much smaller and compact fan and heat sink cooling system. Waste heat is usually exhausted away from the device operator towards the rear or sides of the device. Docking station
Docking station and laptop
A docking station (sometimes referred to simply as a dock) is a laptop accessory that contains multiple ports, and in some cases expansion slots or bays for fixed or removable drives. A laptop connects and disconnects to a docking station, typically through a single large proprietary connector. A docking station is an especially popular laptop accessory in a corporate computing environment, due to a possibility of a docking station to transform a laptop into a full-featured desktop replacement, yet allowing for its easy release. This ability can be advantageous to "road warrior" employees who have to travel frequently for work, and yet who also come into the office.
Charging trolleys
Laptop charging trolleys, also known as laptop trolleys or laptop carts, are mobile storage containers to charge multiple laptops, netbooks, and tablet computers at the same time. The trolleys are used in schools that have replaced their traditional static computer labs suites of desktop equipped with "tower" computers, but do not have enough plug sockets in an individual classroom to charge all of the devices. The trolleys can be wheeled between rooms and classrooms so that all students and teachers in a particular building can access fully charged IT equipment.
Solar panels
In some laptops, solar panels are able to generate enough solar power for the laptop to operate. The One Laptop Per Child Initiative released the OLPC XO-1 laptop which was tested and successfully operated by use of solar panels. Presently, they are designing a OLPC XO-3 laptop with these features. The OLPC XO-3 can operate with 2 watts of electricity because its renewable energy resources generate a total of 4 watts. Samsung has also designed the NC215S solar–powered notebook that will be sold commercially in the U.S. market. Accessories
A common accessory for laptops is a laptop sleeve, laptop skin, or laptop case, which provides a degree of protection from scratches. Sleeves, which are distinguished by being relatively thin and flexible, are most commonly made of neoprene, with sturdier ones made of low-resilience polyurethane. Some laptop sleeves are wrapped in ballistic nylon to provide some measure of waterproofing.
Obsolete features
Features that certain early models of laptops used to have that are not available in most current laptops include:
Reset ("cold restart") button in a hole (needed a thin metal tool to press) Instant power off button in a hole (needed a thin metal tool to press) Integrated charger or power adapter inside the laptop Floppy disk drive Serial port Parallel port Modem Shared PS/2 input device port VHS or 8mm VCR IrDA S-video port[note 1] PC Card / PCMCIA slot ExpressCard slot CD/DVD Drives (starting with 2013 models) VGA port (starting with 2013 models)
Comparison with desktops
Advantages
Portability is usually the first feature mentioned in any comparison of laptops versus desktop PCs. Physical portability allows a laptop to be used in many places—not only at home and at the office, but also during commuting and flights, in coffee shops, in lecture halls and libraries, at clients' locations or at a meeting room, etc. Within a home, portability enables laptop users to move their device from the living room to the dining room to the family room. Portability offers several distinct advantages: Productivity: Using a laptop in places where a desktop PC cannot be used can help employees and students to increase their productivity on work or school tasks. For example, an office worker reading their work e-mails during an hour-long commute by train, or a student doing their homework at the university coffee shop during a break between lectures. Immediacy: Carrying a laptop means having instant access to information, including personal and work files. This allows better collaboration between coworkers or students, as a laptop can be flipped open to look at a report, document, spreadsheet, or presentation anytime and anywhere. Up-to-date information: If a person has more than one desktop PC, a problem of synchronization arises: changes made on one computer are not automatically propagated to the others. There are ways to resolve this problem, including physical transfer of updated files (using a USB flash memory stick or CD-ROMs) or using synchronization software over the Internet, such as cloud computing. However, transporting a single laptop to both locations avoids the problem entirely, as the files exist in a single location and are always up-to-date. Connectivity: In the 2010s, a proliferation of Wi-Fi wireless networks and cellular broadband data services (HSDPA, EVDO and others) in many urban centers, combined with near-ubiquitous Wi-Fi support by modern laptops meant that a laptop could now have easy Internet and local network connectivity while remaining mobile. Wi-Fi networks and laptop programs are especially widespread at university campuses.
Other advantages of laptops:
Size: Laptops are smaller than desktop PCs. This is beneficial when space is at a premium, for example in small apartments and student dorms. When not in use, a laptop can be closed and put away in a desk drawer. Low power consumption: Laptops are several times more power-efficient than desktops. A typical laptop uses 20–120 W, compared to 100–800 W for desktops. This could be particularly beneficial for large businesses, which run hundreds of personal computers thus multiplying the potential savings, and homes where there is a computer running 24/7 (such as a home media server, print server, etc.). Quiet: Laptops are typically much quieter than desktops, due both to the components (quieter, slower 2.5-inch hard drives) and to less heat production leading to use of fewer and slower cooling fans. Battery: a charged laptop can continue to be used in case of a power outage and is not affected by short power interruptions and blackouts. A desktop PC needs an Uninterruptible power supply (UPS) to handle short interruptions, blackouts, and spikes; achieving on-battery time of more than 20–30 minutes for a desktop PC requires a large and expensive UPS. All-in-One: designed to be portable, most 2010-era laptops have all components integrated into the chassis (however, some small laptops may not have an internal CD/CDR/DVD drive, so an external drive needs to be used). For desktops (excluding all-in-ones) this is divided into the desktop "tower" (the unit with the CPU, hard drive, power supply, etc.), keyboard, mouse, display screen, and optional peripherals such as speakers.
Disadvantages
Compared to desktop PCs, laptops have disadvantages in the following areas: Performance
While the performance of mainstream desktops and laptop is comparable, and the cost of laptops has fallen less rapidly than desktops, laptops remain more expensive than desktop PCs at the same performance level.The upper limits of performance of laptops remain much lower than the highest-end desktops (especially "workstation class" machines with two processor sockets), and "bleeding-edge" features usually appear first in desktops and only then, as the underlying technology matures, are adapted to laptops.
For Internet browsing and typical office applications, where the computer spends the majority of its time waiting for the next user input, even relatively low-end laptops (such as Netbooks) can be fast enough for some users. Most higher-end laptops are sufficiently powerful for high- resolution movie playback, some 3D gaming and video editing and encoding. However, laptop processors can be disadvantaged when dealing with a higher-end database, maths, engineering, financial software, virtualization, etc. This is because laptops use the mobile versions of processors to conserve power, and these lag behind desktop chips when it comes to performance. Some manufacturers work around this performance problem by using desktop CPUs for laptops.
Upgradeability
Upgradeability of laptops is very limited compared to desktops, which are thoroughly standardized. In general, hard drives and memory can be upgraded easily. Optical drives and internal expansion cards may be upgraded if they follow an industry standard, but all other internal components, including the motherboard, CPU and graphics, are not always intended to be upgradeable. Intel, Asus, Compal, Quanta and some other laptop manufacturers have created the Common Building Block standard for laptop parts to address some of the inefficiencies caused by the lack of standards. The reasons for limited upgradeability are both technical and economic. There is no industry-wide standard form factor for laptops; each major laptop manufacturer pursues its own proprietary design and construction, with the result that laptops are difficult to upgrade and have high repair costs. Devices such as sound cards, network adapters, hard and optical drives, and numerous other peripherals are available, but these upgrades usually impair the laptop's portability, because they add cables and boxes to the setup and often have to be disconnected and reconnected when the laptop is on the move.
Ergonomics and health effects
Wrists
Laptop cooler (silver) under laptop (white), preventing heating of lap and improving laptop airflow
Prolonged use of laptops can cause repetitive strain injury because of their small, flat keyboard and trackpad pointing devices.Usage of separate, external ergonomic keyboards and pointing devices is recommended to prevent injury when working for long periods of time; they can be connected to a laptop easily by USB or via a docking station. Some health standards require ergonomic keyboards at workplaces.
Neck and spine
A laptop's integrated screen often requires users to lean over for a better view, which can cause neck or spinal injuries. A larger and higher-quality external screen can be connected to almost any laptop to alleviate this and to provide additional screen space for more productive work. Another solution is to use a computer stand.
Possible effect on fertility
A study by State University of New York researchers found that heat generated from laptops can increase the temperature of the lap of male users when balancing the computer on their lap, potentially putting sperm count at risk. The study, which included roughly two dozen men between the ages of 21 and 35, found that the sitting position required to balance a laptop can increase scrotum temperature by as much as 2.1 °C (4 °F). However, further research is needed to determine whether this directly affects male sterility.A later 2010 study of 29 males published in Fertility and Sterility found that men who kept their laptops on their laps experienced scrotal hyperthermia (overheating) in which their scrotal temperatures increased by up to 2.0 °C (4 °F). The resulting heat increase, which could not be offset by a laptop cushion, may increase male infertility.
A common practical solution to this problem is to place the laptop on a table or desk, or to use a book or pillow between the body and the laptop.Another solution is to obtain a cooling unit for the laptop. These are usually USB powered and consist of a hard thin plastic case housing one, two, or three cooling fans – with the entire assembly designed to sit under the laptop in question – which results in the laptop remaining cool to the touch, and greatly reduces laptop heat buildup. Thighs
Heat generated from using a laptop on the lap can also cause skin discoloration on the thighs known as "toasted skin syndrome".
Durability
A clogged heat sink on a laptop after 2.5 years of use
Laptops are generally not durable, however there are certain exceptions.
Laptop keyboard with its keys (except the space bar) removed, revealing crumbs, pet hair and other detritus to be cleaned away.
Equipment wear
Because of their portability, laptops are subject to more wear and physical damage than desktops. Components such as screen hinges, latches, power jacks, and power cords deteriorate gradually from ordinary use, and may have to be replaced. A liquid spill onto the keyboard, a rather minor mishap with a desktop system (given that a basic keyboard costs about US$20), can damage the internals of a laptop and destroy the computer, result in a costly repair or entire replacement of laptops. One study found that a laptop is three times more likely to break during the first year of use than a desktop. To maintain a laptop, it is recommended to clean it every three months for dirt, debris, dust, and food particles. Most cleaning kits consist of a lint-free or microfiber cloth for the LCD screen and keyboard, compressed air for getting dust out of the cooling fan, and cleaning solution. Harsh chemicals such as bleach should not be used to clean a laptop, as they can damage it.
Parts replacement
Original external components are expensive and usually proprietary and non-interchangeable; other parts are inexpensive—a power jack can cost a few dollars—but their replacement may require extensive disassembly and reassembly of the laptop by a technician. Other inexpensive but fragile parts often cannot be purchased separately from larger more expensive components. For example, the video display cable and the backlight power cable that pass through the lid hinges to connect the motherboard to the screen may eventually break from repeated opening and closing of the lid. These tiny cables usually cannot be purchased from the original manufacturer separate from the entire LCD panel, with the price of hundreds of dollars, although for popular models an aftermarket in pulled parts generally exists. The repair costs of a failed motherboard or LCD panel often exceeds the value of a used laptop. Parts can also be ordered from third party vendors.
Heating and cooling
Laptops rely on extremely compact cooling systems involving a fan and heat sink that can fail from blockage caused by accumulated airborne dust and debris. Most laptops do not have any type of removable dust collection filter over the air intake for these cooling systems, resulting in a system that gradually conducts more heat and noise as the years pass. In some cases the laptop starts to overheat even at idle load levels. This dust is usually stuck inside where the fan and heat sink meet, where it can not be removed by a casual cleaning and vacuuming. Most of the time, compressed air can dislodge the dust and debris but may not entirely remove it. After the device is turned on, the loose debris is reaccumulated into the cooling system by the fans. A complete disassembly is usually required to clean the laptop entirely. However, preventative maintenance such as regular cleaning of the heat sink via compressed air can prevent dust build up on the heat sink. Many laptops are difficult to disassemble by the average user and contain components that are sensitive to electrostatic discharge (ESD).
Battery life
Battery life is limited because the capacity drops with time, eventually requiring replacement after as little as a year. A new battery typically stores enough energy to run the laptop for three to five hours, depending on usage, configuration, and power management settings. Yet, as it ages, the battery's energy storage will dissipate progressively until it lasts only a few minutes. The battery is often easily replaceable and a higher capacity model may be obtained for longer charging and discharging time. Some laptops (specifically ultrabooks) do not have the usual removable battery and have to be brought to the service center of its manufacturer or a third- party laptop service center to have its battery replaced. Replacement batteries can also be expensive. Security and privacy
Because they are valuable, commonly used, portable, and easy to hide in a backpack or other type of travel bag, laptops are often stolen. Every day, over 1,600 laptops go missing from U.S. airports.[74] The cost of stolen business or personal data, and of the resulting problems (identity theft, credit card fraud, breach of privacy), can be many times the value of the stolen laptop itself. Consequently, physical protection of laptops and the safeguarding of data contained on them are both of great importance. Most laptops have a Kensington security slot, which can be used to tether them to a desk or other immovable object with a security cable and lock. In addition, modern operating systems and third-party software offer disk encryption functionality, which renders the data on the laptop's hard drive unreadable without a key or a passphrase. As of 2015, some laptops also have additional security elements added, including eye recognition software and fingerprint scanning components.
Modem is short for Modulator Demodulator. It’s an electronic device used to access the Internet that modulates carrier waves to encode information to be transmitted and also demodulates incoming carrier waves to decode the information they carry. What is a modem?
A modem is a very important piece of network hardware that allows a computer to send and receive data through a telephone line or cable connection. In simple words, it’s the device that connects a computer to the Internet.
A modem (Photo Credit : Tmthetom / Wikipedia Commons)
The word modem is actually made by combining parts of two different words – Modulator and demodulator. As this suggests, a modem is a device that both modulates and demodulates signals that encode and retrieve information, respectively. For starters, modulation is a process of adding meaningful information to a carrier wave so that it can be transmitted over long distances.
You see, when an electrical signal containing some meaningful information needs to be transmitted over a long distance, it is added to a carrier wave. This process of ‘mounting’ the original signal on a carrier wave is called modulation.
This is an example of amplitude modulation, wherein the amplitude of the carrier wave is modified proportionally according to the amplitude of the input signal. (Photo Credit : Wikimedia.org) (Photo Credit : upload.wikimedia.org) The Importance of a Modem
Back in the old days, when landline phones were the primary tool to communicate over long distances, modems came in pretty handy to gain Internet connectivity using telephone lines. In fact, without modems, it would have been impossible for most users to connect to the Internet.
While computer technology is purely digital, i.e., it relies on numbers to transmit and receive information, telephone technology, even to this day, is partly analog, meaning that it uses continuously varying electrical signals to transmit information.
Now, we have telephone lines that are partly analog and a lot of computer tech (e.g., laptops, desktops etc.) that is purely digital. How do you make them talk to each other and exchange information?
Simple! Use a modem. A modem has two plugs in it, one that connects it to the telephone line (or the cable provided by your Internet service provider) and the other connecting it to your computer (or a WiFi router).
Typically, two cords connect to the modem – one brings it the Internet, and the other takes the Internet to a router or a computer (Photo Credit : Simon A. Eugster / Wikipedia Commons)
Basically, what the modem does is take the digital signal from the computer and add it on top of an analog telephone signal (i.e., modulates it) so that it can be transferred through the telephone line.
Since your modem sends information through a telephone line by modulating digital signals, it also needs to have another kind of translator that helps it demodulate the analog signals it receives via the telephone line.
That’s why a modem is named as such, because it both modulates and demodulates signals.
It is important to note that you don’t necessarily require a standalone modem to link to the Internet; you can also do that by directly plugging in the Ethernet cable in your computer. Most modern computers have a small inbuilt modem that draws power from the motherboard.
Notice the Ethernet cable at the rear of a computer cabinet. You don’t necessarily need a modem to link to the internet.
This depends on your ISP and how it provides broadband connectivity to its users. Your ISP may provide you an ethernet cable that plugs directly into your computer and helps it communicate with the network digitally, without needing a modem to switch back and forth between analog and digital signals. Modem vs router
It should be noted that if you intend to connect to the Internet wirelessly, or want to get multiple devices connected to the same network, a simple modem won’t be enough. In that case, you will need a different device called a router.
You might have heard the term ‘router’ thrown around a lot in broadband conversations. A router, also referred to as a ‘WiFi router’, is basically a device that lets you connect multiple devices to the Internet through the same physical Internet connection.
A typical wireless router (Photo Credit : Flickr)
A router also lets the connected devices talk to each other over a local network. Furthermore, it offers some protection to the individual devices connected it to by keeping them from being directly exposed to the Internet.
If you want to use the Internet on only one device, then a regular modem should suffice. However, if you want to connect your laptop to the Internet to work and also want to use a messaging app on your phone or tablet, you will need a modem plus a router, wherein the modem will bring Internet to your house and the router will let multiple devices connect to it.
Fortunately, modern routers combine the features of both a regular modem and a router, which means that you don’t need to have two separate devices. In fact, due to the increasing popularity of such routers, some ISPs often provide free routers to their customers when they subscribe to their broadband plans.