Analog & Digital Signals In general, there are two types of telecommunication transmission--Analog transmission and Digital transmission. Analog Transmission Analog transmission uses signals that are exact replicas of a sound wave or picture being transmitted. Signals of varying frequency or amplitude are added to carrier waves with a given frequency of electromagnetic current to produce a continuous electric wave. The term "analog signal" came about because the variations in the carrier waves are similar, or analogous, to that of the voice itself For example, in analog transmission, say a telephone system, an electric current or the reproduction of patterned sound waves are transmitted through a wire and into the telephone receiver. Once this is completed, they are then converted back into sound waves. Digital Transmission In digital transmission the signals are converted into a binary code, which consists of two elements—positive and non-positive. Morse code and the "on and off" flashing of a light are basic examples. Positive is expressed as the number 1, while non-positive is expressed as the number 0. Numbers that are expressed as a string of 0s and 1s are called binary numbers. As an example of digital transmission, in a type of digital telephone system, coded light signals produced by a rapidly flashing laser travels through optical fibers (thin strands of glass) and are then decoded by the receiver. When transmitting a telephone conversation, the light flashes on and off about 450 million times per second. This high rate enables two optical fibers to carry about 15,000 conversations simultaneously. digital transmission is usually faster and involves less noise and disturbances as compared to analog data transmission.
Posted on: Thu, 04 Jul 2013 05:01:52 +0000
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