Thermostatic unit

Claim 1

IN A SELF-CONTAINED AND CONVENTIONALLY SIZED PROPORTIONAL THERMOSTATIC UNIT, THE COMBINATION COMPRISING A SINGLE HOUSING IN WHICH THERE ARE DISPOSED FIRST AND SECOND CONDUCTORS ADAPTED TO RECEIVE A D.C. SUPPLY VOLTAGE THEREBETWEEN; MEANS FOR PRODUCING A D.C. ERROR VOLTAGE WHICH IN POLARITY AND MAGNITUDE CORRESPONDS TO THE SENSE AND EXTENT OF THE DIFFERENCE BETWEEN AN ACTUAL TEMPERATURE AND A DESIRED TEMPERATURE; SAID PRODUCING MEANS INCLUDING A RESISTANCE BRIDGE HAVING INPUT TERMINALS CONNECTED TO SAID CONDUCTORS AND INCLUDING A SET POINT POTENTIOMETER MANUALLY ADJUSTABLE TO REPRESENT THE DESIRED TEMPERATURE, A MANUALLY SET CALIBRATE POTENTIOMETER, AND A TEMPERATURE-SENSITIVE RESISTANCE WHICH IN VALUE REPRESENTS THE ACTUAL TEMPERATURE, A TRANSISTOR AMPLIFIER CONNECTED TO RECEIVE AN OPERATING VOLTAGE FROM SAID CONDUCTORS AND CONNECTED TO RECEIVE SAID ERROR VOLTAGE AS AN INPUT SIGNAL; SAID AMPLIFIER HAVING MEANS INCLUDING A RANGE ADJUST POTENTIOMETER FOR AFFORDING ADJUSTMENTS IN THE GAIN OF THE AMPLIFIER, MEANS INCLUDING A ZERO ADJUST POTENTIOMETER FOR ADJUSTING THE OUTPUT PRODUCED BY THE AMPLIFIER WHEN THE ERROR VOLTAGE IS ZERO, AND AN OUTPUT CIRCUIT WITH MEANS FOR PRODUCING D.C. CURRENT FLOW THERETHROUGH WHICH VARIES ACCORDING TO THE POLARITY AND MAGNITUDE OF SAID ERROR SIGNAL; SUCH CURRENT BEING ADAPTED TO CONTROL AN ELECTRICAL POWER OPERATOR REMOTELY LOCATED FROM THE THERMOSTATIC UNIT.