The field of telecommunication has evolved from a stage when signs, drum beats and semaphores were used for long distance communication to a stage when electrical, radio and Electro- optical signals are being used. Optical signals produced by laser sources and carried by ultra-pure glass fibers are recent additions to the field.
Telecommunication networks carry information signals among entries which are geographically far apart. An entity may be a computer, a human being, facsimile machines, a data terminal and so on. Billions of such entities the world-over are involved in the process of information transfer which may be in the form of telephone conversation or a file transfer between two computers or a message transfer between two terminals, etc.
In telephone conversation, the one who initiates the call is referred to as the calling subscriber and the one for whom the call is destined is the called subscriber. In other cases of information transfer, the communicating entities are known as source and destination, respectively.
Telecommunication networks carry information signals among entries which are geographically far apart. An entity may be a computer, a human being, facsimile machines, a data terminal and so on. Billions of such entities the world-over are involved in the process of information transfer which may be in the form of telephone conversation or a file transfer between two computers or a message transfer between two terminals, etc.
In telephone conversation, the one who initiates the call is referred to as the calling subscriber and the one for whom the call is destined is the called subscriber. In other cases of information transfer, the communicating entities are known as source and destination, respectively.
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