This circuit activates a relay after a time given by C1 and R1. The circuit is from a Radio Electronics from December 1974. The relay voltage is the same as that used in the power supply.
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...