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, for bands above 15 MHz, was found in an Argentine publication from the 1970s. The L1...
May 2017 - The new Wolfspeed 650 V Schottky rectifier diodes can now be purchased from Mouser...
The action of this circuit, found in a 1977 amateur radio documentation, is like to a delay line....