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Home , Category 5 cable, Electrical connector, Modular connector, Parallel communication, Parallel port, Parallel SCSI

Ports

In , a port serves as an between the computer and other or devices. Physically, a port is a specialized outlet on a piece of equipment to which a plug or cable connects. Electronically, the several conductors making up the outlet provide a signal transfer between devices.

The term "port" is derived from a Dutch word "poort" meaning gate, entrance or door.

ETHERNET PORTS:

Ethernet is a family of computer networking technologies for local area networks (LANs) commercially introduced in 1980. Standardized in IEEE 802.3, Ethernet has largely replaced competing wired LAN technologies.

Systems communicating over Ethernet divide a of into individual packets called frames. Each frame contains source and destination addresses and error-checking data so that damaged data can be detected and re-transmitted.

The standards define several wiring and signaling variants. The original 10BASE5 Ethernet used as a shared medium. Later the coaxial cables were replaced by and fiber optic links in conjunction with hubs or switches. Data rates were periodically increased from the original 10 megabits per second, to 100 gigabits per second.

Since its commercial release, Ethernet has retained a good degree of compatibility. Features such as the 48- MAC address and Ethernet frame format have influenced other networking protocols.

HISTORY OF ETHERNET:

Ethernet was developed at Xerox PARC between 1973 and 1974.[1][2] It was inspired by ALOHAnet, which had studied as part of his PhD dissertation.[3] The idea was first documented in a memo that Metcalfe wrote on May 22, 1973.[1][4] In 1975, Xerox filed a patent application listing Metcalfe, David Boggs, Chuck Thacker and Butler Lampson as inventors.[5] In 1976, after the system was deployed at PARC, Metcalfe and Boggs published a seminal paper.

TYPES OF CABLE USED TO CONNECT TO ETHERNET PORTS:

1) Ethernet over twisted pair: Ethernet over twisted pair technologies use twisted-pair cables for the of an Ethernet . Other Ethernet cable standards employ coaxial cable or . Early versions developed in the 1980s included StarLAN followed by 10BASE-T. By the , fast, inexpensive technologies began to emerge. Currently the most popular are 100BASE-TX () and 1000BASE-T (), running at 100 Mbit/s and 1000 Mbit/s (1 Gbit/s), respectively. These standards all use 8P8C connectors.[note 1] Meanwhile higher-speed implementations generally support lower-speed standards inclusively; thus it is possible to mix different generations of equipment. Inclusive capability is designated 10/100 or 10/100/1000- for connections that support such combinations.[1]:123 The cables usually have four pairs of (though 10BASE-T and 100BASE-TX only require two of the pairs). The three standards support both full-duplex and half- duplex communication.

2) (Cat 5): Category 5 cable (Cat 5) is a twisted pair cable for carrying signals. This type of cable is used in for computer networks such as Ethernet. It is also used to carry other signals such as and . The cable is commonly connected using punch down blocks and modular connectors. Most Category 5 cables are unshielded, relying on the twisted pair design and for noise rejection. Category 5 has been superseded by the Category 5e (enhanced) specification.

3)Modular connectors: is the name given to a family of electrical connectors originally used in wiring and now used for many other purposes. Many applications that originally used a bulkier, more expensive connector have now migrated to modular connectors. Probably the most well known applications of modular connectors are for telephone jacks and for Ethernet jacks, both of which are nearly always modular connectors.

Types of modular connectors:

a) 4P4C:

The 4P4C connector, is popularly, but incorrectly, called RJ22, RJ10, or RJ9. It is also commonly referred to as a "Handset Connector" because of the most popular usage for the connector.[5] It is the de facto industry standard for wired telephone handsets. It is used to provide connection from the base of the telephone to the handset.This handset connector is actually not a at all, since it was never intended to connect directly to the telephone service lines: RJ connects a phone to the service lines, while 4P4C connects two parts of a phone. Other RJ connector wiring standards are used by telephone companies. The 4P4C is only used for an end user application from the phone to the handset.

b) 6P6C: The 6P2C, 6P4C, and 6P6C modular connectors are probably most well known for their use as RJ11, RJ14, and RJ25 registered jacks respectively. RJ11 is a physical interface often used for terminating telephone wires. It is probably the most familiar of the registered jacks, being used for single line POTS telephone jacks in most homes across the world.

RJ14 is similar, but for two lines, and RJ25 is for three lines. RJ61 is a similar registered jack for four lines. The cord and its plug are more often a true RJ11 with only two conductors. Modular plugs are described as containing a number of potential contact "positions" and the actual number of contacts installed within these positions. RJ11, RJ14, and RJ25 all use the same six-position modular connector, thus are physically identical except for the different number of contacts (two, four and six respectively). c) 8P8C: The 8P8C (8 position 8 contact, also backronymed as 8 position 8 conductor) is a modular connector commonly used to terminate twisted pair and multiconductor flat cable. These connectors are commonly used for Ethernet over twisted pair, registered jacks and other telephone applications, RS-232 serial using the EIA/TIA 561 and Yost standards, and other applications involving unshielded twisted pair, shielded twisted pair, and multiconductor flat cable. Although commonly referred to as an "RJ45" in the context of Ethernet and category 5 cables, it is incorrect to refer to a generic 8P8C connector as an RJ45.[9][10][11][12] A telephone-system- standard RJ45 plug has a key which excludes insertion in an un-keyed 8P8C socket. [13] The registered jack (RJ) standard specifies a different mechanical interface and wiring scheme for an RJ45S from TIA/EIA-568-B which is often used for modular connectors used in Ethernet and telephone applications. 8P8C modular plugs and jacks look very similar to the plugs and jacks used for FCC's registered jack RJ45 variants, although the RJ45S is not compatible with 8P8C modular connectors.

IEEE 1394 interface ports:

The IEEE 1394 interface, developed in late 1980s and early 1990s by Apple as FireWire, is a serial interface standard for high-speed communications and isochronous real-time data transfer. The 1394 interface is comparable with USB and often those two technologies are considered together, though USB has more market share.[1] Apple first included FireWire in some of its 1999 models, and most Apple computers since the year 2000 have included FireWire ports, though, as of 2012, nothing beyond the 800 version (IEEE-1394b).[2] The interface is also known by the brand i.LINK (Sony), and Lynx (). IEEE 1394 replaced parallel SCSI in many applications, because of lower implementation costs and a simplified, more adaptable cabling system. The 1394 standard also defines a interface, though this is not as widely used.

IEEE 1394 is the High-Definition Audio-Video Network Alliance (HANA) standard connection interface for A/V (audio/visual) component communication and control. FireWire is also available in , fiber optic, and coaxial versions using the isochronous protocols.

STANDARDS AND VERSIONS

The previous standards and its three published amendments are now incorporated into a superseding standard, IEEE 1394-2008. The features individually added give a good history on the development .

FireWire 400 (IEEE 1394-1995)

The original release of IEEE 1394-1995[ specified what is now known as FireWire 400. It can transfer data between devices at 100, 200, or 400 Mbit/s half-duplex data rates (the actual transfer rates are 98.304, 196.608, and 393.216 Mbit/s, i.e., 12.288, 24.576 and 49.152 per second respectively).These different transfer modes are commonly referred to as S100, S200, and S400.

Cable length is limited to 4.5 metres (14.8 ft), although up to 16 cables can be daisy chained using active repeaters; external hubs, or internal hubs are often present in FireWire equipment. The S400 standard limits any configuration's maximum cable length to 72 metres (236 ft). The 6-conductor connector is commonly found on desktop computers, and can supply the connected device with power.

The 6-conductor powered connector, now referred to as an alpha connector, adds power output to support external devices. Typically a device can pull about 7 to 8 watts from the port; however, the voltage varies significantly from different devices. Voltage is specified as unregulated and should nominally be about 25 volts (range 24 to 30). Apple's implementation on is typically related to battery power and can be as low as 9 V.

Improvements (IEEE 1394a-2000)

An amendment, IEEE 1394a, was released in 2000,which clarified and improved the original specification. It added support for asynchronous streaming, quicker bus reconfiguration, packet concatenation, and a power-saving suspend mode.

IEEE 1394a offers a couple of advantages over IEEE 1394. 1394a is capable of arbitration accelerations, allowing the bus to accelerate arbitration cycles to improve efficiency. It also allows for arbitrated short bus reset, in which a can be added or dropped without causing a big drop in isochronous transmission.

1394a also standardized the 4-conductor alpha connector developed by Sony and trademarked as "i.LINK", already widely in use on consumer devices such as camcorders, most PC laptops, a number of PC desktops, and other small FireWire devices. The 4-conductor connector is fully data-compatible with 6-conductor alpha interfaces but lacks power connectors.

FireWire 800 (IEEE 1394b-2002)

IEEE 1394b-2002 introduced FireWire 800 (Apple's name for the 9-conductor "S800 bilingual" version of the IEEE 1394b standard). This specification and corresponding products allow a transfer rate of 786.432 Mbit/s full-duplex via a new encoding scheme termed beta mode. It is backwards compatible with the slower rates and 6-conductor alpha connectors of FireWire 400. However, while the IEEE 1394a and IEEE 1394b standards are compatible, FireWire 800's connector, referred to as a beta connector, is different from FireWire 400's alpha connectors, making legacy cables incompatible. A bilingual cable allows the connection of older devices to the newer port. In 2003, Apple was the first to introduce commercial products with the new connector.

FireWire S1600 and S3200

In December 2007, the 1394 Trade Association announced that products would be available before the end of 2008 using the S1600 and S3200 modes that, for the most part, had already been defined in 1394b and was further clarified in IEEE Std. 1394-2008. The 1.6 Gbit/s and 3.2 Gbit/s devices use the same 9-conductor beta connectors as the existing FireWire 800 and will be fully compatible with existing S400 and S800 devices. It will compete with the forthcoming USB 3.0. S1600 (Symwave]) and S3200 (Dap Technology) development units have been made, however because of FPGA technology DapTechnology targeted S1600 implementations first with S3200 not becoming commercially available until 2012.

FireWire S800T (IEEE 1394c-2006)

IEEE 1394c-2006 was published on June 8, 2007.

It provided a major technical improvement, namely new port specification that provides 800 Mbit/s over the same 8P8C (Ethernet) connectors with Category 5e cable, which is specified in IEEE 802.3 clause 40 (gigabit Ethernet over copper twisted pair) along with a corresponding automatic negotiation that allows the same port to connect to either IEEE Std 1394 or IEEE 802.3 (Ethernet) devices.

Though the potential for a combined Ethernet and FireWire 8P8C port is intriguing, as of November 2008, there are no products or which include this capability.

Parallel port:

A is a type of interface found on computers (personal and otherwise) for connecting various . In computing, a parallel port is a physical interface. It is also known as a port or Centronics port. The IEEE 1284 standard defines the bi-directional version of the port, which allows the transmission and reception of data at the same time.

HISTORY:

The Centronics Model 101 printer was introduced in 1970 and included the first parallel interface for printers.[1] The interface was developed by Robert Howard and Prentice Robinson at Centronics. The Centronics parallel interface quickly became a de facto industry standard; manufacturers of the time tended to use various connectors on the system side, so a variety of cables were required. For example, early VAX systems used a DC-37 connector, NCR used the 36-pin micro ribbon connector, Texas Instruments used a 25-pin card and used a 50-pin micro ribbon connector.Dataproducts introduced a very different implementation of the parallel interface for their printers. It used a DC-37 connector on the side and a 50 pin connector on the printer side—either a DD-50 (sometimes incorrectly referred to as a "DB50") or the block shaped M-50 connector; the M-50 was also referred to as Winchester.[2][3] Dataproducts parallel was available in a short-line for connections up to 50 feet (15 m) and a long-line version for connections from 50 feet (15 m) to 500 feet (150 m). The Dataproducts interface was found on many mainframe systems up through the 1990s, and many printer manufacturers offered the Dataproducts interface as an option.

IBM released the IBM in 1981 and included a variant of the Centronics interface— only IBM logo printers (rebranded from Epson) could be used with the IBM PC.[4] IBM standardized the parallel cable with a DB25F connector on the PC side and the Centronics connector on the printer side. Vendors soon released printers compatible with both standard Centronics and the IBM implementation.

IBM implemented an early form of bidirectional interface in 1987. HP introduced their version of bidirectional, known as Bitronics, on the LaserJet 4 in 1992. The Bitronics and Centronics interfaces were superseded by the IEEE 1284 standard in 1994.

Pinouts:Pinouts for parallel port connecters are given below in fig.

PS/2 connector:

The PS/2 connector is a 6-pin Mini-DIN connector used for connecting some keyboards and mice to a PC compatible computer system. Its name comes from the IBM Personal System/2 series of personal computers, with which it was introduced in 1987. The PS/2 mouse connector generally replaced the older DE-9 RS-232 "serial mouse" connector, while the PS/2 keyboard connector replaced the larger 5- pin/180° DIN connector used in the IBM PC/AT design. The PS/2 designs on keyboard and mouse interfaces are electrically similar and employ the same . However, a given system's keyboard and mouse port may not be interchangeable since the two devices use a different set of commands.

Pinouts: Pinouts for PS/2 are as in fig.

Serial Ports:

In computing, a is a physical interface through which information transfers in or out one bit at a time (in contrast to a parallel port). Throughout most of the history of personal computers, data transfer through serial ports connected the computer to devices such as terminals and various peripherals.While such interfaces as Ethernet, FireWire, and USB all send data as a serial stream, the term "serial port" usually identifies hardware more or less compliant to the RS-232 standard, intended to interface with a or with a similar communication device.

Modern computers without serial ports may require serial-to-USB converters to allow compatibility with RS 232 serial devices. Serial ports are still used in applications such as industrial automation systems, scientific instruments, shop till systems and some industrial and consumer products. computers may use a serial port as a control console for diagnostics. Network equipment (such as routers and switches) often use serial console for configuration. Serial ports are still used in these areas as they are simple, cheap and their console functions are highly standardized and widespread. A serial port requires very little supporting software from the host system.

HARDWARE OF SERIAL PORT:

Some computers, such as the IBM PC, used an called a UART, that converted characters to (and from) asynchronous serial form, and automatically looked after the timing and framing of data. Very low-cost systems, such as some early home computers, would instead use the CPU to send the data through an output pin, using the so-called bit-banging technique. Before large-scale integration (LSI) UART integrated circuits were common, a or microcomputer would have a serial port made of multiple small-scale integrated circuits to implement shift registers, logic gates, counters, and all the other logic for a serial port.

Early home computers often had proprietary serial ports with pinouts and voltage levels incompatible with RS-232. Inter-operation with RS-232 devices may be impossible as the serial port cannot withstand the voltage levels produced and may have other differences that "lock in" the user to products of a particular manufacturer.

Low-cost processors now allow higher-speed, but more complex, serial communication standards such as USB and FireWire to replace RS-232. These make it possible to connect devices that would not have operated feasibly over slower serial connections, such as mass storage, sound, and video devices.

Many personal computer still have at least one serial port, even if accessible only through a pin header. Small-form-factor systems and laptops may omit RS-232 connector ports to conserve space, but the electronics are still there. RS-232 has been standard for so long that the circuits needed to control a serial port became very cheap and often exist on a single , sometimes also with circuitry for a parallel port. Universal Serial Bus:

Universal Serial Bus (USB) is an industry standard developed in the mid-1990s that defines the cables, connectors and communications protocols used in a bus for connection, communication and power supply between computers and electronic devices.

USB was designed to standardize the connection of computer peripherals, such as keyboards, pointing devices, digital cameras, printers, portable media players, disk drives and network adapters to personal computers, both to communicate and to supply electric power. It has become commonplace on other devices, such as , PDAs and video game consoles.USB has effectively replaced a variety of earlier interfaces, such as serial and parallel ports, as well as separate power chargers for portable devices.

As of 2008, approximately 6 billion USB ports and interfaces were in the global marketplace, and about 2 billion were being sold each year.

HISTORY:

A group of seven companies began development on USB in 1994: Compaq, DEC, IBM, Intel, , NEC and Nortel. The goal was to make it fundamentally easier to connect external devices to PCs by replacing the multitude of connectors at the back of PCs, addressing the usability issues of existing interfaces, and simplifying software configuration of all devices connected to USB, as well as permitting greater data rates for external devices. The first silicon for USB was made by Intel in 1995.

The original USB 1.0 specification, which was introduced in January 1996, defined data transfer rates of 1.5 Mbit/s "Low Speed" and 12 Mbit/s "Full Speed".[5] The first widely used version of USB was 1.1, which was released in September 1998. The 12 Mbit/s data rate was intended for higher-speed devices such as disk drives, and the lower 1.5 Mbit/s rate for low data rate devices such as

The USB 2.0 specification was released in April 2000 and was ratified by the USB Implementers Forum (USB-IF) at the end of 2001. Hewlett-Packard, Intel, Lucent Technologies (now Alcatel-Lucent), NEC and Philips jointly led the initiative to develop a higher data transfer rate, with the resulting specification achieving 480 Mbit/s, a fortyfold increase over the original USB 1.1 specification.

The USB 3.0 specification was published on 12 November 2008. Its main goals were to increase the data transfer rate (up to 5 Gbit/s), to decrease power consumption, to increase power output, and to be backwards-compatible with USB 2.0. USB 3.0 includes a new, higher speed bus called SuperSpeed in parallel with the USB 2.0 bus.[8] For this reason, the new version is also called SuperSpeed.The first USB 3.0 equipped devices were presented in January 2010.

SCSI:

Small Computer System Interface is a set of standards for physically connecting and transferring data between computers and peripheral devices. The SCSI standards define commands, protocols, and electrical and optical interfaces. SCSI is most commonly used for hard disks and tape drives, but it can connect a wide range of other devices, including scanners and CD drives, although not all controllers can handle all devices. The SCSI standard defines command sets for specific peripheral device types; the presence of "unknown" as one of these types means that in theory it can be used as an interface to almost any device, but the standard is highly pragmatic and addressed toward commercial requirements.

SCSI is an intelligent, peripheral, buffered, peer to peer interface. It hides the complexity of physical format. Every device attaches to the SCSI bus in a similar manner. Up to 8 or 16 devices can be attached to a single bus. There can be any number of hosts and peripheral devices but there should be at least one host. SCSI uses handshake signals between devices, SCSI-1, SCSI-2 have the option of parity error checking. Starting with SCSI-U160 (part of SCSI-3) all commands and data are error checked by a CRC32 checksum. The SCSI protocol defines communication from host to host, host to a peripheral device, peripheral device to a peripheral device. However most peripheral devices are exclusively SCSI targets, incapable of acting as SCSI initiators—unable to initiate SCSI transactions themselves. Therefore peripheral-to-peripheral communications are uncommon, but possible in most SCSI applications. The Symbios Logic 53C810 chip is an example of a PCI host interface that can act as a SCSI target.

Cabling:

SCSI Parallel Interface

Internal parallel SCSI cables are usually ribbons, with two or more 50–, 68–, or 80–pin connectors attached. External cables are typically shielded (but may not be), with 50– or 69–pin connectors at each end, depending upon the specific SCSI bus width supported.[22] The 80–pin Single Connector Attachment (SCA) is typically used for hot-pluggable devices, where external cables are not usually required.

Serial attached SCSI

Serial attached SCSI uses a modified Serial ATA data and power cable. iSCSI iSCSI ( Small Computer System Interface) usually uses Ethernet connectors and cables as its physical transport, but can run over any physical transport capable of transporting IP.

USB Attached SCSI

USB Attached SCSI allows SCSI devices to use the Universal Serial Bus.

Automation/Drive Interface

The Automation/Drive Interface − Transport Protocol (ADT) is used to connect devices, such as tape drives, with the controllers of the libraries (automation devices) in which they are installed. The ADI standard specifies the use of RS-422 for the physical connections. The second-generation ADT-2 standard defines iADT, use of the ADT protocol over IP (Internet Protocol) connections, such as over Ethernet. The Automation/Drive Interface − Commands standards (ADC, ADC-2, and ADC-3) define SCSI commands for these installations.

Digital Visual Interface (DVI) is a video display interface developed by the Digital Display Working Group (DDWG). The digital interface is used to connect a video source to a display device, such as a .

DVI was developed to create an industry standard for the transfer of digital video content. The interface is designed to transmit uncompressed digital video and can be configured to support multiple modes such as DVI-D (digital only), DVI-A (analog only), or DVI-I (digital and analog). Featuring support for analog connections as well, the DVI specification provides optional compatibility with the VGA interface.[1] This compatibility along with other advantages led to widespread acceptance in the PC industry over other competing digital standards such as Plug and Display (P&D) and Digital Flat Panel (DFP).[2] Though predominantly found in computer devices, DVI is also present in some consumer electronics such as television sets.

Single-link DVI

A single-link DVI connection consists of four TMDS links; each link transmits data from the source to the device over 1 twisted pair. Three of the links correspond to the RGB components of the video signal: red, green, blue (for a total of 24 bits per pixel.) The fourth link carries the pixel clock. The binary data is encoded using 8b10b encoding. The 8b10b encoding system serves several purposes: it preserves DC balance over time, it generates sufficient signal transitions to maintain receiver bit-alignment (pixel clock recovery), and it provides symbol () alignment. Each TMDS link carries binary data at ten times the pixel clock reference , for a maximum data rate of 1.65 Gbit/s × 3 data pairs for single-link DVI.

DVI does not use packetisation, but rather transmits the pixel data as if it were a rasterized analog video signal. As such, during each vertical refresh period, the complete frame is 'drawn' over the DVI link. The full active area of each frame is always transmitted; no is used, and there is no support for only transmitting changed parts of the image. Video modes typically use horizontal and vertical refresh timings that are compatible with CRT displays, but this is not a requirement. The DVI specification (see below for link) does, however, include a paragraph on "Conversion to Selective Refresh" (under 1.2.2), suggesting this feature for future devices. The DVI specification mandates a maximum pixel clock frequency of 165 MHz when running in single- link mode. With a single DVI link, the highest supported standard resolution is 2.75 megapixels (including blanking interval) at 60 Hz refresh. For practical purposes, this allows a maximum screen resolution at 60 Hz of 1,915 × 1,436 pixels (standard 4:3 ratio), 1,854 × 1,483 pixels (5:4 ratio), or 2,098 × 1,311 (widescreen 16:10 ratio).

Dual-link DVI

To support display devices requiring higher video , there is provision for a dual DVI link. A dual link doubles the number of TMDS pairs, effectively doubling video bandwidth at a given pixel clock frequency. The DVI specification mandates how the dual link may be used. All display modes that use a pixel clock below 165 MHz, and have at most 24 bits per pixel, are required to use single-link mode. All modes that require more than 24 bits per pixel, and/or 165 MHz pixel clock frequency must use dual-link mode. In modes where each pixel uses 24 bits of color data per pixel or less and dual-link mode is in use, the transmitter stripes pixel data across both links; each sequential video pixel is transmitted on alternate links. In modes with color depth greater than 24 bits per pixel, the second link carries the least significant bits of each pixel. Pinout for DVI is as below:

VGA connector

A (VGA) connector is a three-row 15-pin DE-15 connector. The 15-pin VGA connector is found on many video cards, computer monitors, and some high definition television sets. On computers or other small devices, a mini-VGA port is sometimes used in place of the full-sized VGA connector.

DE-15 is also conventionally called RGB connector, D-sub 15, mini sub D15, mini D15, DB-15, HDB-15, HD-15 or HD15 (High Density, to distinguish it from the older and less flexible DE-9 connector used on some older VGA cards, which has the same shell size but only two rows of pins).

VGA connectors and cables carry analog component RGBHV (red, green, blue, horizontal sync, vertical sync) video signals, and VESA Display Data Channel (VESA DDC) data. In the original version of DE-15 pinout, one pin was keyed and 4 pins carried Monitor ID bits which were rarely used; VESA DDC redefined some of these pins and replaced the key pin with +5 V DC power supply.

PINOUT:

TRS connector:

A TRS connector (tip, ring, sleeve) is a common family of connector typically used for analog signals including audio. It is cylindrical in shape, typically with three contacts, although sometimes with two (a TS connector) or four (a TRRS connector).

It is also termed an audio jack, phone jack, phone plug, and jack plug. Specific models are termed stereo plug, mini-jack, mini-stereo, headphone jack, tiny telephone connector and bantam plug.

The TRS connector was invented for use in telephone switchboards in the 20th century and is still widely 1 used, both in its original ⁄4 in (exactly 6.35 mm) size and in miniaturized versions: 3.5 mm (approx. 1 3 ⁄8 in) and 2.5 mm (approx. ⁄32 in). The connector's name is an initialism derived from the names of three conducting parts of the plug: Tip, Ring, and Sleeve — hence, TRS.

In the UK, the terms jack plug and jack socket are commonly used for the respective male and female TRS connectors. In the U.S., a stationary (more fixed) is called a "jack". The terms phone plug and phone jack are sometimes used to refer to TRS connectors, but are also sometimes used colloquially to refer to RJ11 and older telephone plugs and the corresponding jacks that connect wired to wall outlets (the similar terms phono plug and phono jack refer to RCA connectors though both plug types are used in tandem when a computer or MP3 player connects to a stereo). In conversation, the diameter is often added to specify which size — quarter-inch phone plug or 3.5 mm phone jack for the unbalanced two-channel three-contact version, and balanced TRS jack or TRS phone plug for the balanced one-channel three-contact version.

Tip-ring-sleeve terminology

In twisted pair wiring to this day, the non-inverting and/or "live" (or "hot") wire of each pair is termed the ring, while the inverting and/or "earthy" (or "neutral") wire is termed the tip, inherited from the traditional connection via the TRS connector in telephone systems. If the pair is shielded, or if the pair is accompanied by a dedicated earth wire, this third conductor is termed the sleeve. This usage corresponds to the connection to a three-connector jack plug in a manual .