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 interesting sensor for RF signals was found in an article in the June 1989 Radio Electronics...
The frequency of this oscillator depends on the inductor and capacitors in parallel with it. In...
This circuit was found in RCA and General Electric documentation from the 1980s. The circuit has...