The circuit shown is from old English documentation and can be made with BC548 transistors for low power ones. The 2N3055 must be mounted on a heat radiator.
This circuit is from American documentation from the 70s. Transistors are not common today, but...
Found in old documentation, this simple test checks both the polarity and the existence of voltage...
This circuit is from a 1987 American publication called Electronics Handbook. The circuit can be...