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 an electrical circuit. This quantity is known as the peak-to-average ratio (p/a r or PAR). 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.