AUDIO FREQUENCY AUTOMATIC MUTING ARRANGEMENTS

摘要

IMPROVEMENTS IN OR RELATING TO AUDIO FREQUENCY AUTOMATIC MUTING ARRANGEMENTS In an automatic audio frequency muting arrangement, intelligence and noise signals in a received audio frequency signal are detected and the levels of the detected intelligence and noise signals are compared. The result of this comparison controls a muting switch in the audio frequency path. The intelligence signals are detected by a capacitive time constant circuit which is of relatively short time constant, and the noise signals are detected by a capacitive time constant circuit of relatively long time constant. The time constant capacitor for noise signal detection can be isolated from the input during those times in which intelligence signals are present in the received audio frequency signal.