Found in old American documentation, this circuit is intended for the control of heating elements. The SCR must have current according to the controlled load. Transistors are from the time.
This sensor was published in Radio Electronics magazine in April 1962. The two-transistor circuit...
Another of the many similar configurations we have in this section. This one is from a Radio...
This circuit like the previous one is intended for 24V x 3W solenoids being connected from the...