This circuit was found in an American documentation from the 90s. It consists of a variable with a triac in which the load current can be controlled, monitored by an ammeter.
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...