This variable oscillator with power step for alarms was found in an American documentation from the 90's. The power transistor must be equipped with a heat sink.
We found this simple transistor tester in a French publication in 1981. It uses a common analog...
Who is faster? or reaction game are other names for this circuit that we find in old...
This circuit is from an 80's component manual. The components are from the time, but the circuit...