Brown, Boveri & Co., Ag

Gary Winkler

Richard W Brown

Method for detecting the presence or absence of an audio-frequency signal (V.sub.T) superimposed on a power supply network, the audio-frequency signal (V.sub.T) having a known frequency (f.sub.T) and an amplitude (A.sub.T) lying within a permissible range of amplitudes (.DELTA.A.sub.T), where the power supply network transmits a signal mixture (V) containing a fundamental (V.sub.g, f.sub.g, A.sub.g), harmonic frequencies (V.sub.H, f.sub.H, A.sub.H) thereof and interference frequencies (V.sub.S, f.sub.S, A.sub.S), which includes, with a microcomputer (M.sub.C), generating a signal at the same point on adjacent waves of the fundamental (V.sub.g);

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Minneapolis, MN, United States of America

Gary Winkler