Abstract: An input control system having a sensing circuit, a switching circuit and a source of power isolated from the sensing circuit and the switching circuit. The sensing circuit includes a sensor having a variable electrical characteristic, a detector for detecting variations in that characteristic and for producing a representative output, a signal producing circuit for producing a predetermined signal in response to the detector output achieving a selected value, and coupler responsive to the predetermined signal to produce a coupling output. The switching circuit which is isolated from the sensing circuit produces a switching signal in response to the coupling signal to operate a switch for connecting an electrical load to the power source.