This circuit was found in an Electronics World of 1968. Its purpose in triggering a relay when the circuit receives signals from a vibration sensor. The circuit is used in emergency situations.
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....