This “people detector” with pyroelectric sensor was found in the April 1991 issue of Radio Electronics magazine. The circuit is based on an LM324 and a sensor from that time.
This circuit triggers the LED when the monitored battery voltage drops below 9 V for 12 V...
We found this circuit in a Radio Electronics from January 1967. The SCR is already the C106, which...
This power source with silicon diodes at a time when valves were still used was found in Radio...