Interkom als Alarmsystem (Sprachgesteuerter Schalter, VOX mit LM324)

The usual method of measuring the har- monic distortion of an audio amplifier is to feed it with an extremely pure sine wave signal and to measure the harmonic products introduced by the amplifier. Unfortunately, few commercially available signal generators have distortion figures better than 0.05%, and since modern audio amplifiers better this figure most of the distortion measured will be that produced by the generator.