This alarm circuit was found in April 1975 Radio Electronics magazine. The circuit uses a 12 V power supply and relay but can be modified to work with other voltages.
With this circuit, a relay can be activated from an alternating signal with frequency up to a few...
With this circuit the visually impaired can easily locate important places inside the house, such...
In the figure we have the way to use the transistors of an old-paired pair as a trigger circuit. The...