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 assumes that a pulse produced by S1 has a constant duration determined by R1 and C1....
This circuit was found in a 90s Electronic Design. It uses integrated circuits that are not common...
This receiver for the citizen's band was found in the Radio Electronics magazine of June 1952. The...