This circuit is intended to detect when current flows through the opening of a car door. The circuit fires the horn for 90 seconds. The FET can be the BF245 and the NPN transistors can be the BD135.
This circuit is from an old American publication. The indicated transistor is oversized as the 15 V...
This power source can supply currents in the range of 100 mA to 1 A, depending on the transformer and the...
This circuit was found in an American magazine 73 for radio amateurs of the 80s. It is an...