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 oscillator was found in a 1967 General Electric documentation. The UJT is P-channel, an unusual...
Found in an Elektor from the 90s, this circuit triggers a Sonalert-type buzzer when the sensor is...
This precision circuit can provide timings from 0.2 milliseconds to 3 minutes accurately. The...