This alarm goes off if someone leaves a door open. We found it in the Encyclopedia of Electronic Circuits Volume 5 from 1995. The circuit uses components that are still common today.
This beat frequency oscillator or BFO was found in an American 1980s documentation. The circuit is...
We found this setting in the Texas Instruments opto-electronics manual. The bipolar can be the...
This bistable control uses a 4069 as bistable. The circuit can drive relays up to 100 mA with the...