This circuit was obtained from the 1995 Encyclopedia of Electronic Circuits Volume 5. The circuit uses a CMOS 4001 and has a transistor power stage.
With the configuration shown in the figure, we have the relay being activated when the microphone picks...
This TTL generator that can function as a control shield or external clock for microcontrollers was found in...
The OP07 operational amplifier is not common today, as the circuit is from an old European manual....