What is a Communication? The following picture shows a sample communications system. As illustrated in this figure, communications systems contain all types of devices. An example of a communications system. Some devices that can serve as sending and receiving devices are (a) personal computers, (b) notebook computers, (c) Web-enabled cellular telephones, (d) Web-enabled handheld computers, (e) MSN TV, and (f) GPS receivers. The communications channel consists of telephone lines, underground cables, microwave stations, and satellites. The primary function of a communications device, such as a modem, is to convert or format signals so they are suitable for the communications channel or a receiving device. When using a telephone line as the communications channel, you need a modem to convert between analog and digital signals. An analog signal consists of acontinuous electrical wave. Computers, however, process data as digital signals. A digital signal consists of individual electrical pulses that represent the bits grouped together into bytes. For instance, a modem connected to a sending computer converts the computer’s digital signals into analog signals. The analog signals then travel over a communications channel, such as a standard telephone line. At the receiving end, another modem converts the analog signals back into digital signals that a receiving computer can recognize.
Posted on: Sun, 07 Jul 2013 16:09:07 +0000
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