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 powerful sound emitter used in defense to intimidate people was found in a 90s Popular...
The circuit shown in the figure triggers a relay when S1 is pressed, but this only in the absence of...
This small receiver for the medium wave range was found in Radio Electronics magazine from July...