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.
We found this circuit in a Mullard manual from 1960. The transistor is a phototransistor of the...
The circuit that gave rise to this configuration was found in a magazine of the 1980s with the...
This oscillator with FET was found in Popular Electronics from the 90s. This traditional...