This simple circuit, found in American documentation, uses only one relay that locks when any of the sensors is activated. To reset, simply turn off the power for a moment.
This configuration with the LM383 appears elsewhere on this site. The circuit shown was obtained...
This circuit was found in National Semiconductor documentation from the 1990s. It has cold...
This simulation shows how to use an operational amplifier as a voltage comparator. The sample uses the...