This circuit was found in the February 1985 issue of Radio Electronics magazine. It is based on an AY-3-1350 melody generator that was common at the time. It is suitable for analog lines only.
This circuit, found in a 1988 documentation consisting of an audio switch that turns off the load...
This stabilized source can supply currents up to 200 mA with the indicated transistor or 500 mA...
With the shadow over the sensor, it is possible to interrupt the sound of your amplifier using this...