The integrated circuit used is uncommon today. We found this configuration in Motorola's 1990 Linear Databook. The triac can be any of the TIC series.
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...