This simple transistor tester was found in a Japanese magazine in 1967. It tests general purpose transistors of both the NPN and PNP type and is powered by 4 batteries (6 V).
This circuit triggers a Sonalarme when the LED used as a sensor receives light. The circuit was...
Found on a 1969 EDN this circuit switches a current from a digital control signal. The impedance...
We found this circuit in a 1985 technical publication. The circuit uses PUTs to drive lamps....