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 was found in Radio Electronics from the 90s. The transistor is for general use. The...
We found this circuit in a 2005 Linear Technology application manual. The circuit makes use of a...
This circuit is from 1971 American documentation. Transistors are still common except for 2N2060...