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 regulation of high voltages through common semiconductor circuits, such as integrated circuits and...
The LM2904 is not very common today, but common comparators and operationals can be used in the...
This amplifier circuit was found in a Radio Electronics from April 1959. The circuit needs only 20 mV...