Thursday, June 28, 2012

How does a Video Telephone Work?

            A video telephone is a communication device used foe simultaneous exchange of visual images and the associated speech. In this system one can see the face of the person talking at the other end and also listen to his voice. Do you know how this is possible?

Video Telephone

            A complete video telephone system consists of the following parts:

1.                   Terminal equipment which has a camera display screen microphone and a speaker phone. These instruments transform both voice and visual inputs into electrical signals and vice versa.
2.                  Transmission facilities which carry the electrical signals up to long distances.
3.                  A switching system to allow a choice of terminals to be interconnected. At the transmission point, voice and picture both are converted into electrical signals. Which are carried to a long distance through transmission arrangement? At the receiver end these signals are converted into voice and picture which can be heard and seen by the person at the receiver end.

            Video telephone system was developed in 1927 by H.E. lves who transmitted one way images by wire from Washington D.C. also transmitted from blew jersey to New York by radio. These experiments were aimed at transmitting and reproducing a recognizable human face.

            In 1930, lves demonstrated a two-way video telephone over a wire path in New York City. From 1936 to 1940, a public video telephone service was provided on a local and intercity basis by the German post offices. Call could be set up by appointment between any two subscribers in Berlin, Leipzig, Nuremberg and Munich. A similar system was inaugurated by the soviets in 1961 for subscribers in 8 cities, including Moscow, Kiew and Leningrad.

            Since the 1960s, most major communication agencies throughout the world have been exploring the feasibility of a commercial video telephone service. The first limited commercial video telephone service was offered in the early 1970s by bell system.

            In this system, ordinary telephone wires utilizing specially designed repeaters were used to transmit the video signals. Video requires two pairs of wires, one for each direction of transmission. Early service between Chicago and Pittsburgh provided valuable insight into customer needs, but customer acceptance did not meet the early expectation.

            Nowadays, researchers have developed video telephone systems, using communication satellite links. In many developed countries, this system has now become popular after vase improvement of its mechanism in terms of perfection at the level of customer’s expectation.

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