Telecommunication Essay Research Paper Telecommunication1 IntroductionComputer and — страница 2

movement of the rod in the coil produced a weak electric current. An advantage was that theoretically it could also be used both as a transmitter and a receiver. But since the current produced was so weak, it was unsuccessful as a transmitter. Most modern day telephones still use a variation of Bell’s design. The first practical transmitter was invented by Thomas Edison while he was working for the Western Union. During his experiments Edison noticed that certain carbon compounds change their electrical resistance when subjected to varying pressure. So he sandwiched a carbon button between a metal membrane and a metal support. The motion of the membrane changed the pressure on the carbon button, varying the flow of electricity through the microphone. When the Bell Vs. Western

Union lawsuit was settled the rights to this transmitter were also taken over by Bell. 2.3. Please Wait, I’ll Connect You. The first network of telephones consisted of switchboards. When a customer wanted to place a call he would turn a crank on his telephone terminal at home. This would produce a current through the line. A light at the switchboard would light up. The caller would tell the operator where he wanted to call and she would connect him by means of inserting a plug into a jack corresponding to the desired phone. In earlier years he found that he could use the ground as the return part of the circuit, but this left the telephone very susceptible to interference from anything electrical. So in the mid 1880s Bell realized that he would have to change the telephone

networks from one wire to two wire. In 1889 Almon Brown Strowger invented the telephone dial which eliminated the use for telephone operators. 2.4. The Free Press Reported That President Carter……. French inventor Emile Baudot created the first efficient printing telegraph. The printing telegraph was the first to use a typewriter like keyboard and allowed eight users to use the same line. More importantly, his machines did not use Morse code. Baudot’s five level code sent five pulses for each character transmitted. The machines did the encoding and decoding, eliminating the need for operators. After some improvements by Donald Murray the rights to the machine were sold to Western Union and Western Electric. The machine was named the teletypewriter and was also known by

it’s nickname TTY. A service called telex was offered by Western Union. It allowed subscribers to exchange typed messages with one another. 3. From The Carterfone to the 14,400 3.1. I’ll Patch Her Up On The Carterfone, Captain. The first practical computers used the means of punched cards as a method of storing data. These punched cards held 80 characters each. They dated back to the mechanical vote-counting machine invented by Hermen Hollerith in 1890. But this type of computer was very hard and expensive to operate. They were very slow in computing speed and the punch cards could be very easily lost or destroyed. One of the first VDTs (Video Display Terminal) was the Lear- Siegler ADM-3A. It could display 24 lines of 80 characters each (a remarkable feat of technology). One

of the regulations that AT&T passed was that no other company’s equipment could be physically connected to any of it’s lines or equipment. This meant that unless AT&T invented a peripheral it would not be legal to connected to the telephone jack. In 1966 a small Texas company called Carterfone invented a simple device that could go around these regulations. The Carterfone allowed for a company’s radio to be connected to the telephone system. The top portion of the Carterfone consisted of molded plastic. When a radio user needed to use the telephone, the radio operator at the base station placed the receiver in the Carterfone and dialed the number. This allowed the user to call through the radio. AT&T challenged the integrity of the Carterfone on the phone lines

and lost the battle in court. In 1975 the FCC passed Part 68 rules. They were specifications that, if met would allow third party companies to sell and hook up their equipment to the telephone network. This turned the telephone industry upside down and challenged AT&T’s monopoly in the telephone business. 3.2. So Gentelmen A’ Will Be 65 With more and more electronic communication and the invention of VDTs the shortcomings of the Baudot code were realized. So in 1966, several telecommunications companies devised a replacement for the Baudot code. The result was the American Standard Code for Information Interchange, or ASCII. ASCII uses 7 bits of code, allowing it to represent 128 characters without a shift code. The code defined 96 printable characters (A through Z in