Telecommunication covers various methods used for communication of information at a distance. Telecommunication includes Telegraphy, Telephony, Facsimile, Television, Telemetering, Radar, Internet, etc. In all these systems the information is carried out in the form of electric signals. In this chapter only telegraphy has been described.
Telegraphy is used to transfer information in the written form. It is a combination of two words “Tele” means at a distance and “Graph” means to write. Hence telegraphy is to write at a distance. In the early days of civilization, there were various methods of transferring information (messages) over long distances these methods went on improving with the passage of time and today we have the most modern methods of communication.
Telegraphy was the first electrical communication system that allowed the people to communicate with each other beyond the limited ranges of voice and vision. Telegraphy depends upon the transmission of electrical signals, which are arranged according to some definite code. The information to be sent is first converted into some form of code for ease of transmission and reception. Codes are symbols that represent units of information understandable by both sender and receiver.
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