Audio Powered Tape Recorder Switching Controller

When the source of the sound is only intermittently exist, it’s better to turn on the tape recording only when it really present.  We can control a tape recorder to switch a tape recorder on when audio is present by driving an IRF511 power MOSFET and rectifying the audio input. To record intermittent transmissions such as repeater output, aircraft, etc, the following circuit was used with a communications receiver. Here is the schematic diagram of the circuit: