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 circuit is from 1990 documentation. When we press D1 the lamp remains on for a time interval that...
This 1995 circuit uses interruption sensors or NC connected in series in any quantity. With the...
This circuit from a Radio Electronics magazine from June 1969 already shows the use of the newly...