This circuit is from a March 1967 Radio Electronics. The circuit applies to general purpose SCRs such as the TIC106, C106 and others. The test is done by increasing the gate voltage to the trigger point.
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...