Distortion

In telecommunication, the term distortion has the following meanings:

1. In a system or device, any departure of the output signal waveform from that which should result from the input signal waveform's being operated on by the system's specified, i.e. , ideal, transfer function.

Note: Distortion may result from many mechanisms. Examples include nonlinearities in the transfer function of an active device[?], such as a vacuum tube, transistor, or operational amplifier. Distortion may also be caused by a passive component such as a coaxial cable or optical fiber, or by inhomogeneities, reflections, etc., in the propagation path.

2. In start-stop teletypewriter signaling, the shifting of the significant instants of the signal pulses from their proper positions relative to the beginning of the start pulse.

Note: The magnitude of the distortion is expressed in percent of an ideal unit pulse length.

Source: from Federal Standard 1037C and from MIL-STD-188