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 was originally developed in 1989 to allow the triggering of loads from audio signals...
A circuit in which the light turns on smoothly and goes out quickly, but which can be adjusted more...
Found in old documentation, this circuit is intended for low level amplitude modulation with low...