Found in a 90s English documentation, this circuit consists of an RF detector for testing in RF stages. The diode can any germanium type.
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....