We found this circuit in the 1964 RCA transistors manual. The transistors used are uncommon today, but they can be used equivalent. The circuit controls the operation of a heating element.
The circuit shown is from an old European publication. In it we have the way to activate a relay...
We found this circuit in a European publication from the 1990s. Transistors are still common types...
This circuit was found in an American documentation and can be added to common amplifiers of any...