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.
The circuit below was suggested by the Motorola Linear Databook of 1990. The component used is...
This circuit is intended for testing small capacitors. What we have is an astable multivibrator, which works...
This circuit was found in an American 1980s documentation. The transistorized step is the...