This circuit detects when an audio signal exceeds a certain level or even occurs due to an object falling, a door slamming or other. The circuit is from a Radio Electronics from January 1980.
In the figure we have a regulator circuit for output voltages of 0.5 to 10 V with currents up to...
This transmitter influences an oscillator that modulates the transmitting stage and at the same...
We find this simple circuit in an English publication called Electronic Circuit Design on spring 3 of...