This circuit is for 12 V batteries but can be used with batteries of other voltages by changing the zener diode. The trigger point is adjusted by R1. The operating system accepts equivalents.
This circuit is from an article in the December 1988 issue of Radio Electronics magazine that...
This circuit was found in an American documentation from the 80's. The sensor is a special...
The FET can be a BF245, and the other transistors can be the BC548 and BC558 in this simple AM...