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 sensitive photo-diode circuit with output compatible with TTL logic was found in a 1972 RCA...
This circuit can send signals in both the VHF and FMN bands with a range of a few tens of meters. The...
This circuit was found in a Popular Electronics from the 80s. It is possible to control a relay...