ISSN 2321 3361 © 2019 IJESC Research Article Volume 9 Issue No.9 A Compact Telecommunication System for Apartment Chandam Thoisana Singh BE Student Department of Electronics & Communication Engineering Manipur Institute of Technology, Manipur, India Abstract: This paper presents a multifunction and a multi-useful device that can be widely applicable and can be easily installed and handled by an ordinary person. In this paper the system i.e. A Compact Telecommunication System for Apartment is used as an EPABX (Electronic Private Automatic Branch Exchange) which maintains the privacy. Keywords: EPABX, Opto-isolation, Timer, Relay, Tone decoder, BCD to ten line decoder, Switches, IVRS. I. INTRODUCTION: They set the rates the phone companies could charge and determined that services and equipment each could offer. This As with many innovations, the idea for the telephone came stayed in effect until AT&T’s forced divestiture in 1984, the along far sooner than it was brought to reality. While Italian conclusion of a U.S. Department of Justice anti-trust suit that innovator Antonia Meucci is credited with inventing the first had been filed in 1974. The all powerful company had become basic phone in 1849, and Frenchman Charles Bourseul devised popularly known and disparaged as “Ma Bell.” AT&T’s local a phone in 1854, Alexander Graham Bell won the first U.S operations were divided into seven independent Regional Bell patent for the device in 1876. Bell began his research in 1874 Operating Companies, known as the “Baby Bells.” AT&T and had financial backers who gave him the best business plan became a long-distance-services company. By 1948, the 30 for bringing it to the market. In 1877-1878, the first telephone millionth phone was connected in the United States; by the line was constructed, the first switchboard was created and the 1960’s there were more than 80 million phone hookups in the telephone exchange was in operation. Three years later, almost U.S. and the and 160 million in the world by 1980, there were 49,000 telephone in use. In 1880, Bell merged this company more than 175 million telephone subscriber lines in the U.S. with others to form the American Bell Telephone Company In 1993, the first digital cellular network went online in and in 1885 American Telegraph and Telephone Company Orlando, Florida; by 1995 there were 25 million cellular (AT&T) was formed; it dominated telephone communications phone subscribers, and that number exploded at the turn of the for the next century. At one point in time, Bell system century, with digital cellular phone service expected to replace employees purposely denigrated the U.S telephone system to land-line phones for most U.S. customers by as early as 2010. drive down stock prices of all phone companies and thus make We have designed an interesting, simple and cheap system i.e. it easier for Bell to acquire smaller competitors. By 1900 there A Compact Telecommunication System for Apartment which were nearly 600,000 phones in Bell’s telephone system; that aims at providing a private branch exchange with secrecy. The number shot up to 2.2 million phones by 1905, and 5.8 million system which we have designed is very simple and reliable by 1910. In 1915 the transcontinental telephone line began and has many advantages over the existing ones. With the use operating. By 1907, AT&T had a near monopoly on phone of IVRS and voice mail the system can be upgraded and use in and telegraph service, thanks to its purchase of Western various applications. Union. Its president, Theodore Vail, urged at the time that a monopoly could most effectively operate the nation’s far-flung II. BLOCK DIAGRAM: communications network. At the urging of the public and AT&T competitors, the government began to investigate the company for anti-trust violations, thus forcing the 1913 Kingsbury commitment, an agreement between AT&T vice president Nathan Kingsbury and the office of the U.S. Attorney General. Under this commitment, AT&T agreed to divest itself of Western Union and provide long-distance services to independent phone exchanges. During the World War I, the government nationalized telephone and the telegraph lines in the United States from June 1918 to July 1919, when, after a joint resolution of Congress, President Wilson issued an order putting them under the direction of the U.S Post office. A year later, the systems were returned to private ownership, AT&T resumed its monopolistic hold, and by 1934 the government again acted, this time agreeing to allow it to operate as a regulated monopoly under the “ ” jurisdiction of the FCC. Public utility commissions in state Figure.1. Block diagram of the System. and local jurisdictions were appointed regulators of AT&T and the nation’s independent phone companies, while the FCC Opto-isolation: It is used for optical or electrical isolation regulated long-distance service conducted across states lines. between two systems having different power supply voltage. IJESC, September 2019 23648 http://ijesc.org/ Moreover, it literally performs the function of interfacing IV. WORKING OF THE SYSTEM: between telephone line and our circuit (+6V) without direct electrically contact instead of only electrical coupling in our As shown in the figure1 this system is capable of handling 9 system. When a calling subscriber dials the called subscriber telephone (using a single telephone line pair) located at 9 number followed by extension number, the opto-coupler different locations, let us consider a distance of 90metre from detects the ring signal on the phone line by using opto-coupler each other, for receiving and making outgoing calls, while MCT2E. maintaining secret conversation. This system is useful when a Timer: Opto-coupler activates the “ON Timer” for 10 second single telephone line is to be shared by more members only. The duration of the timer depends during on the residing in different apartments. Suppose, if someone connects fabrication of the circuit and the selection of the timer 9 telephones in parallel, ring signals are heard in all the 9 components. This timer duration introduces some delay telephones (it is also possible that the phones will not work required by the calling subscriber for pressing ‘*’ button (to due to higher load), and out of 9 persons 8 will find that the activate the phone in the tone mode) and extension number, call is not for them. Further, one can overhear others say 1, within 10 sec. The timer is built around NE555 IC along conversation, which is not desirable. To overcome this with its necessary external components. problem, we have design the circuit as the ring is heard only in Relay: The output of the timer energizes relay and this the desired extension, suppose, extension number ‘1’. For particular relay is the heart of the circuit activation. When this making use of this facility, the calling subscriber is required to relay is energized, the processing circuit is connected to +6V initially dial the normal phone number of the called subscriber. supply and other contact of the relay is used to provide loop- When the call is established, no ring back sound is heard by resistance to de-energize the ringer relay in the telephone the calling person. The calling subscriber has then to press the exchange to cut off the ring. ‘*’ key on the telephone to activate the tone mode (if the Tone decoder: When the caller dials the extension number phone normally works in dial mode) and dial extension say 1, 2, 3, 4, 5…………………., 9 in tone mode, this tone number, say, ‘1’, within 10 seconds (in case the calling receiver blocks the output digital codes say “0001”, “0010” subscriber fails to dial the required extension number within ,……………..”1001’, respectively which will be the input of 10 seconds, the line will be disconnected automatically). Also, the next block. We use IC CM8870 which works on 3.58 MHz if the dialed extension phone is not lifted within 10 seconds, oscillating frequency for this application. the ring back sound will stop ringing. The incoming call signal BCD to ten line decoder: The 4-bit output of the previous on the main telephone line is detected by opto-coupler MCT- block is used to convert 10-line decimal. The particular input 2E (IC1), which in turn activates the 10 second “on timer”, line of this decoder excites the respective output (high). To formed by IC2 (NE555) and energize relay RL10 (6V, 100 implement this we used IC CD4028. ohms, 2C/O). One of the ‘N/O’ contacts of the relay has been Switches: The output of the BCD decoder switch on the used to connect +6V rail to the processing circuitry and the respective thyristors and its associated relays. The relays in other has been used to provide 220 ohms loop resistance to de- turn connect the 50Hz extension ring signal derived from the energize the ringer relay in telephone exchange, to cut off the transformer. DIAC conducts above 35V, the ON telephone ring. If the caller dials the extension number suppose ‘1’ in receive only rest of the half of the signal blocked by diode and tone mode, tone receiver CM8870 (IC3) outputs code ‘0001’, DIAC. As soon as the telephone is lifted the phone line which is fed to the 4-bit BCD –to-10 line decimal decoder IC4 voltage shoots up to +48V; and DIAC & DIODE connected in (CD4028). The output of IC4 at its output pin 14 (Q1) goes series with the phone conduct. Besides this, the another high and switches on the SCR (TH-1) and associated relay opto-coupler starts operating and its output is connected to the RL1.