This circuit was found in the Electronics Experimenter Handbook of 1961. The circuit uses door sensors and others. It is powered by 12 V from the car battery.
The integrated circuit used is a voltage reference from Motorola. This configuration was obtained in...
This circuit is from a Radio Electronics from October 1970. The circuit uses transistors from that...
This circuit was obtained from a 1977 magazine, but can still be mounted using BC548 for TR1 and...