This circuit was obtained from 1967 documentation. It uses a sensor to determine the trigger point. The components are of the time, difficulty to obtain these days.
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...