This alarm circuit with NC sensors in series was taken from an article in Radio Electronics magazine from May 1971. The SCR can be any of the 106 series.
This circuit is one of many that the reader can find in this section for testing crystals. The...
I found this circuit on a December 1976 Radio Elettronica. The Italian magazine no longer exists, but...
June 2017 - Mouser Electronics has in stock the new AC Metallized Polypropylene Film Capacitors...