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 interesting shield circuit was obtained from a Poptronics of February 2001. The American...
This vox was found in Hughes documentation from 1968. The circuit uses components from the era. A...
This circuit shows how to use a 3-terminal voltage regulator as a low frequency oscillator by...