Par meter

A peak-to-average ratio meter (Par meter) is a device used to measure the ratio of the peak power level to the time-averaged power level in a circuit. This quantity is known as the peak-to-average ratio (p/a r). Such meters are used as a quick means to identify degraded telephone channels.

Par meters are very sensitive to envelope delay distortion[?]. They may also be used for idle channel noise, nonlinear distortion[?], and amplitude-distortion measurements.

The peak-to-average ratio can be determined for many signal parameters, such as voltage, current, power, frequency, and phase.

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