This circuit was found in the April 1971 Radio Electronics magazine. It uses common transistors and can be adapted to use an LED or audible indicator instead of a light bulb.
The purpose of this circuit is to convert a short-lived pulse into a negative rectangular pulse. The...
This circuit using current components was found in an old documentation. It is a sequential circuit...
This circuit beeps when the sensor is triggered by the opening of the freezer door or other...