This circuit was obtained from ancient American documentation based on the application of neon lamps. The SCR is according to the controlled load. It really is a power control.
This good quality audio amplifier with an output of about 10 W with the original transistor was...
The presented circuit can be implemented with a BC548 and for larger currents a BD135 can be used....
When the input voltage is higher than 2/3 of the power supply voltage the green LEDs glows. When...