This circuit was found in an EDN from the 90s. The circuit employs a double 555 and uses the courtesy light switches of the car as sensors.
This commercial circuit is from a Japanese magazine from 1967. It uses germanium transistors, and...
This circuit can be used to drive relays, solenoids, motors and other loads according the...
This circuit is based on the small keychain that responded to the sound of a whistle and were...