This rapid response amplifier uses an integrated one that is not common today but can be implemented with modern equivalents. The circuit is from an 80's manufacturer documentation.
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....