This series and parallel sensor circuit was found in Popular Electronics from the 1990s. Any SCR can be used and the supply voltage depends on the load.
This circuit, extensively explored in this section and in circuits on this site, is recommended to...
I found this circuit on a December 1976 Radio Elettronica. The Italian magazine no longer exists, but...
We found this circuit in an American documentation of the 80's, being indicated for the test of...