This circuit with the HA2400 was found in the March 1980 Radio Electronics magazine. The circuit has digital-gain control and must be powered by a symmetrical 15 V source.
This alarm goes off if someone leaves a door open. We found it in the Encyclopedia of Electronic...
The pulse duration is determined by the 100k resistor and the separation by the 1M resistor. The...
This circuit uses high voltage transistors to provide direct power from the 110 V power grid or a...