Found in American documentation from the 90's, this circuit is very current and can be implemented with transistors of general use. Never use a power supply without a transformer.
This circuit controls a relay causing it to open and close its contacts at a speed that depends on the...
This circuit is from an Electronics World of 1968. The transistors are of the time and the power...
This circuit is from a Motorola manual from the 70s. The circuit can be implemented with more...