Found in a Philips documentation from 1968, this circuit detects the trimpot set input voltage. The operational can be of almost any kind.
This commercial circuit is from a Japanese magazine from 1967. It uses germanium transistors, and...
This circuit can be used to drive relays, solenoids, motors and other loads according the...
This circuit is based on the small keychain that responded to the sound of a whistle and were...