Coding and Modulation.

The article provides information on modulation in a digital communication system. Modulation is the process of altering the signal parameters of a high frequency carrier, frequency or phase, in relation to a modulated signal, the baseband signal. Demodulation is an additional modulation procedure to reclaim the signal in the baseband. A binary 1 is represented by a "high" signal and a binary 0 is represented by a "low" signal. In "differential coding" every binary 1 to be transmitted causes a change in the signal level, whereas the signal level remains unchanged for a binary zero.