ABSTRACT
Communication systems are used to enable the exchange of data between two or more entities (humans or machines). As can be seen from Figure 1.1, data consists of a representation of an information source, whose transformation is performed by a source encoder. An example of a source encoder is a thermometer, which converts temperatures (information source) into voltages (data). A telephone can also be viewed as a source encoder, which converts the analog voice (information source) into a voltage (data) before being transmitted along the telephone network (transmission medium). In case the information source is analog and the transmission medium is digital, a CODEC (coder and decoder) is employed to perform the digitization. A VOCODER (voice coder) is a codec speci†c for voice, whose functionality consists of converting analog voice into digital at the transmitter side and the reciprocal at the receiver side.
