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.
These integrated ones consist of class B amplifiers with gain fixed 24 internally for better...
I found this circuit in a 1978 publication. The circuit can be assembled with a BD136 transistor to...
This circuit was found in a Popular Electronics from the 90s. The circuit with the 555 monitors the...