Using LM3909 integrated circuits, this circuit was found in an American documentation from the 90's. The frequencies can be changed by changing the capacitors.
This circuit makes use of high voltage transistors and can be connected to the 110 V (117 V)...
The opening of the sensor in this circuit of the 70's causes an integrated buzzer of the Sonalert type...
The circuit shown is from the component's datasheet, allowing the control of stepper motors up to...