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TYPES OF TYPES OF ANALOG ANALOG TRANSMISSIONS TRANSMISSIONS
There are two basic kinds of analog transmission, both based on how they modulate data to combine an input signal with a carrier signal. Usually, this carrier signal is a specific frequency , and data is transmitted through its variations. The two techniques are amplitude modulation (AM), which varies the amplitude of the carrier signal, and frequency modulation (FM), which modulates the frequency of the carrier. Most analog transmissions fall into one of several categories. Until recently, most telephony and voice communication was primarily analog in nature, as was most television and radio transmission. Early telecommunication devices utilized analogto-digital conversion devices called AUGUST
modulator/demodulators, or modems , to convert analog data to digital data and back. Analog transmission is still very popular, in particular for shorter distances, due to significantly lower costs and complex multiplexing and timing equipment is unnecessary, and in small "short-haul" systems that simply do not need multiplexed digital transmission. However, in situations where a signal often has high signal-to-noise ratio and cannot achieve source linearity, or in long distance , high output systems, analog is unattractive due to attenuation problems. Furthermore, as digital techniques continue to be refined, analog systems are increasingly becoming legacy equipment.
15
The Highly Circulated Satellite Magazine
2010