In this 2001 circuit we have the way to trigger an SCR with a phototransistor. The circuit appears elsewhere in this section, obtained from publications from different eras.
This circuit is from 1968 documentation. We can assemble it with more modern components such as a...
Found in a 90s Silicon Chip documentation this circuit is intended to protect a speaker system in...
The UVTRON tube is an ultraviolet radiation sensor. In this circuit from Radio Electronics from...