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 VCO makes use of components from the 1980s. The circuit can be implemented with modern...
This circuit uses an LDR as a sensor to trigger an LED indicator at a preset lighting level. The...
This circuit was found in a 1968 General Electric documentation. It has an input impedance of 2 M ohms...