Found in old documentation, this circuit makes use of amplifiers of the time, uncommon today. Next to the diagram, the formula for calculating the components.
This circuit is temperature stabilized. Modern equivalent transistors can be used, and the power...
This circuit uses an optocoupler to obtain a solid state relay whose power depends on the Triac...
This power step for relay activation was found in the 1964 RCA transistors manual. The circuit is of the...