Electronic device for subtracting signals and associated system employing such device

摘要

An electronic device comprises separate channels for receiving input signals representative of an undesired signal and a composite signal, envelope detectors for detecting amplitude envelopes of signals representative of the input signals, and an electronic subtractor for determining the electronic difference between the envelope signals to produce an output signal indicative of a desired signal. The device is employed particularly for cancelling the effect of the telephone sidetone signal in a telephone to yield an output signal indicative of the telephone maintone signal.