This circuit was found in a Popular Electronics from the 90s. The circuit has temperature compensation. Coil and capacitors depend on the frequency at which the circuit will be used.
Found in a Philips documentation from 1968, this circuit detects the trimpot set input voltage....
This circuit can be connected to the output of alarms or sirens with the 555, CMOS or TTL,...
This simple capacitor tester, already covered in other articles in this section and on the...