The RCA integrated circuit used in this control is uncommon today. The circuit is from an Electronics Now from July 1995. The sensor determines the value of the adjustment potentiometer.
This circuit locks when the sensors are opened. The relay can be 6 or 12 V depending on the power...
This is a conventional differentiator configuration with operational amplifier. In principle any...
This circuit should be used with low frequency signals only. The circuit is from a documentation from the...