Inthe transmitter there are two common kinds of transmitters: the carbontransmitter, and the electret transmitter. The carbon transmitter uses carbongranules between metal plates called, electrodes, with one consisting of a thindiaphragm that moves by pressure from sound waves and transmits them to thecarbon granules. These electrodes conduct electricity flowing through thecarbon. The sound waves hit the diaphragm causing the electrical resistance ofthe carbon to vary.
The electret transmitter is composed of a thin disk ofmetal-coated plastic held above a thicker, hollow metal disk. This plastic diskis electrically charged, and creates an electric field. The sound waves fromthe caller’s voice cause the plastic disk to vibrate, changing the distancebetween the disks, thus changing the intensity of the electric field. Thesevariations are translated into an electric current which travels across thetelephone lines. The receiver of a telephone is composed of a flat ring ofmagnetic material.
Underneath this magnetic ring is a coil of wire where theelectric current flows. Here, the current and magnetic field from the magnetcause a diaphragm between the two to vibrate, and replicate the sounds that aretransformed into electricity. The telephone is also composed of an alerter and a dial. The alerter,usually known as the ringer, alerts a person of a telephone call, created by aspecial frequency of electricity sent by the telephone number typed in. Thedial is the region on the phone where numbers are pushed or dialed. There aretwo types of dialing systems; the rotary dial, and the Touch-Tone.
The rotarydial is a movable circular plate with the numbers one to nine, and zero. TheTouch-Tone system uses buttons that are pushed, instead of the rotary that sendpulses. The telephone was said to be invented by many people. However, thefirst to achieve this success, although by accident, was Alexander Graham Bell.
He and his associate were planning to conduct an experiment, when Mr. Bell spiltacid on himself in another room, and his associate clearly heard the firsttelephone message: “Mr. Watson, come here; I want you. ” Although AlexanderGraham Bell had invented the telephone, his case had to be defended in courtmore than 600 times for this to be proven. After the invention of the telephone, many other great technologicaladvances were made, which boosted the telephone into a worldwide affair. Thefirst great advance was the invention of automatic switching.
Next, longdistance telephone calls were established in small steps. For example, fromcity to city, across a country, and across the ocean. Following this, underseacable and satellites, which made it possible to link points halfway around theearth sounding as if from next door. Finally, by adding three digit area codes,all phone calls, either to next door or around the world, could be done by thecaller. The first telephone company to establish a telephone industry was theBell Telephone Company, in 1877, by Alexander Graham Bell.
This did last forsometime, however, independent telephone companies were started in many citiesand small towns. By 1908, many customers were being served by a new companycalled AT&T, which eventually bought out the Bell Company. Since it was costlyto have the wires run to a household, many residential people often shared lines,which is called a party line. Although these lines were cheaper for thecustomers, it was a nuisance because only one person could use the phone at atime, and other households could listen in on the calls.
Finally, the price oflocal calls was relatively low, however, long-distance calls were placedrelatively high when compared to the local telephone bill. Today, approximately 95% of the households across North America havetelephones, which is creating a huge opportunity for companies that providelocal and long-distance service. Although prices for calls are slowlydecreasing, the competition between companies is increasing. This can be seenfrom advertisements on television and in the newspaper. And not only is thiscompeting going to continue, it will increase as new technology is discovered.
What is in store for the future? No one will now. However, some of thelatest futuristic ideas that will soon be upon us are; television screens soonaccompany the telephone, so that the caller can see who he or she is having aconversation with. Also, having all of the copper wire replaced with fiberoptics will greatly increase the telephones capabilities. This will give us theadvantage of sending very large pieces of information over the phone line.
Theonly thing that we do know about the telephone, is that it sure has come a longway since its first discovery by the inventor Alexander Graham Bell. A man whowill always be remembered.