why analog communication is used for telephones

Analog and Digital Communication - The concept of information is central to communication. There is no precise definition of the word "information". So, instead of information, we deal with "message". Message is defined as the physical manifestation of information as p..

The concept of information is central to communication. There is no precise definition of the word "information". So, instead of information, we deal with "message..

The transmission lines used in telephony are of two kinds: open- wire and cable. The open-wire lines are gradually being superseded by cable construction, either overhead or underground, for two principal reasons. In the first place, many more circuits can be accommodated-there is a stand..

.e., facsimile of printed matter or pictures) use a similar mechanism. In the case of intercontinental telecommunication, two or more satellites are linked together. High frequency radio and submarine cable systems have been widely used for long- distance overseas telecommunicat..

The area of the Earth from which a satellite is visible increases with the altitude. So, satellites at higher altitudes give larger coverage. At altitudes below 10,000 km, the number of satellites required for global coverage would be excessive. At altitudes above 20,000 km, the time taken by signa..

Two-way operation is essential for satisfactory telephone service, and many of the problems of the industry arise from this fact. A simplified circuit for obtaining two-way operation is shown in the below figure. This is called a local-battery system because a separate battery is required..

What is the Difference Between Digital and Analog Signals? - A computer performs its tasks by turning on and off a series of electronic switches represented by the numerical digits of 0 and 1. A 0 is the code for off, and a 1 is the code for on. Combinations of these digital codes represe..

Communication Satellites - Communication satellites are normally geostationary satellites. They have devices called transponder which receive signals from an earth station and transmit them in different directions. The signals in the form of electromagnetic radiation are transmi..

AIDS - AIDS is a disease that can prove to be fatal. The immune system of the body is affected. Acquired Immuno Deficiency Syndrome which is the medical expansion for AIDS was first detected in June 1981 in USA. The disease is caused by a retrovirus - HIV (human immuno deficiency virus). Immune res..