Found in a 1965 CQ magazine, this circuit uses period components. The unijunction transistor can be a 2N2646 and the relay has voltage according to the supply.
This circuit for telecommunications was found in a 1987 documentation. Connected to the...
This circuit is from a 1966 American documentation. The circuit uses a photo-FET, an unusual...
Currents up to 1.5 A can be regulated with this circuit. The resistor R that determines the...