This circuit is intended to switch high frequency antennas using common diodes. The circuit is from an 80's documentation appearing in other versions in this same section of the site.
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....