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 article is from an old publication from 1978. The transistor can be a BC548 and the power...
This modulated siren has frequency adjustment and modulation in the trimpots. For 220V use 1N4007 as...
Found in a 1958’s publication, this receiver uses components that are nbot easy to find in our...