This circuit is from an 80's documentation, firing when the input voltage exceeds 5 V. The SCR can be the TIC106 need not have a heatsink.
This setting appears multiple times on the site from different sources. This is from a 2000 manual...
This circuit is a shield for microcontrollers and computers drivind high power loads. In the...
July 13, 2015 - Mouser Electronics, Inc. today announced that it has signed a global distribution...