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.
Because it uses TTL integrated circuits, this siren must be powered by 5 V or as indicated with D1 to...
The correct connection of speakers and tweeters in a speaker to obtain better sound quality,...
The CMOS PLL used on this circuit is not very common. The circuit can be used to take out contact...