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.
Found in a 1960 Sylvania manual, this circuit can be implemented with a modern equivalent...
This configuration, already presented in other points of this section and website, is of a...
We found this precise crystal oscillator for the 144 MHz band, depending on the crystal used. The...