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.
The presented circuit uses an operational amplifier that is uncommon nowadays, but it can be...
This circuit is powered by only 3 V and can flash white LEDs from 3.2 to 3.6 V, as it includes a voltage...
This circuit is suggested by National Semiconductor and is based on an LM1578-A integrated circuit...