This circuit makes use of a low impedance microphone. The relay is according to the supply voltage which can be between 9 and 15 V. The operational gain is approximately 100.
The figure shows the basic circuit of a relaxation oscillator with operational amplifier. The...
This circuit was obtained from American documentation from 1966. It triggers when the two input...
Found in an American 1980s documentation, this circuit generates high-intensity pulses for a...