This alarm siren circuit has a latch. We found it in an article in the January 1975 Radio Electronics magazine. Note the power given by Rx and the speaker. It can be increased by changing Q1.
The integrated 4017, a C-MOS counter, is one of the most popular in the design of sequences,...
This simple very low power circuit can be used in a battery powered infrared tone trigger. We...
This timer controls two relays, each with a different timing, activated separately. The circuit is from...