Alternatives to RMS are peak value, peak-to-peak value, and average value. The average value is also known as MAD (Mean Absolute Deviation) or ARV (Average Rectified Value). Instruments for AC measurements using simple diode rectifiers yield the average value of AC waveforms. Prior to the emergence of feasible solid-state RMS-to-DC converters, such instruments were re-calibrated for RMS using a sine-wave test signal; all other waveforms were inaccurate.