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 circuit can be used as a shield for transmitting the temperature of a sensor. The circuit is from...
We found this circuit in an old manual. The bypass range is 20 MHz and the power supply must be...
This small audio amplifier uses germanium transistors and a 12 V supply. The circuit is from a...