Distortion occurring on communication lines due to the different propagation speeds of signals at different frequencies, measured in microseconds of delay relative to the delay at 1700Hz. (This type of distortion does not affect voice communication, but can seriously impair data transmission.)

The distortion of an analog signal as it passes through a transmission medium which is the result of the fact that different frequencies travel through the medium at slightly different speeds.

The change in a signal from the transmitting end to the receiving end resulting from the tendency of some frequency components within a channel to take longer to be propagated than others.