This latched alarm uses a double relay for this purpose and can control higher power external loads like a siren. The circuit is from 1974 documentation and has a very low consumption.
Suggested by National Semiconductor in documentation from the 90s, this circuit uses a switched...
This capacitive switch or approximation relay was found in a 1980s US publication. Power should...
We found this conventional version of a single-transistor oscillator in the January 1996 issue of...