in this sense allows the relative phase of distant signals to be computed. Signal processing In signal processing a pulse or finite wavetrain can be considered as a signal of a single frequency modulated by an envelope, or as a superposition of an infinite number of infinitesimal waves of different frequencies. In the first case, one may speak of the phase of the wave with respect to the envelope as the absolute phase. In the second picture, it is a question of the relative phase of the component frequencies. For examples of physical effects due to the phase of signals with the same power spectrum. References Wave mechanics