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.
This circuit consists of a booster for the medium wave band. We found it in an English publication from...
This circuit converts signals from the 350 kHz to 500 kHz longwave (VLF) band to the 4.35 to 4.6...
This circuit of old documentation can be implemented with modern operational amplifiers. The...