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 circuit was found in a 1967 Delco Radio documentation. The circuit has an input voltage of 250...
We found this simple oscillator in a 1977 amateur radio documentation. It can oscillate up to 30...
We found this circuit in a European publication from the 1970s. The transistors are made of...