Found in an 80's Elektor, this circuit can use any equivalent optical coupler. The buzzer is of the Sonalert type with included oscillator.
We found this circuit in a 90s Electronic Design. The circuit is based on a quadruple operational...
Vox or sonic switch is a relay activated by the voice or any sound picked up by the microphone. This...
This is the traditional source using the LM317 3-terminal regulator circuit. The same source can...