This circuit uses a transistor to trigger the alarm from a low quiescent current sensor. The relay is 12 V. The circuit is from Radio Electronics magazine, April 1975.
This sequential circuit of LEDs was found in a Popular Electronics from the 90s. The circuit can be...
Indicated for 12 V systems, this circuit was obtained in a 90s Siliconix documentation. The...
This circuit for light modulated in frequency (FM) operating at 50 kHz was found in a 90’s...