Signal-activated recording

This circuit ensures that messages received by a radio or transceiver are automatically recorded on a cassette or tape recorder. lt is assumed that the relevant receiver has a squelch (or 'mute') function, and that It is on stand-by on a particular frequency you wish to monitor. The cassette recorder is also switched on, and permanently switched to recording mode. When the message is over, the circuit waits for a couple of seconds, and then switches the recorder off.