Temperature control circuit

Claim 1

A TEMPERATURE SENSING AND CONTROL CIRCUIT FOR AUTOMATICALLY CONTROLLING AND MAINTAINING THE TEMPERATURE OF A DEVICE AT AN ADJUSTABLE, PRESELECTED LEVEL, SAID TEMPERATURE SENSING AND CONTROL CIRCUIT COMPRISING: A SOURCE OF POTENTIAL; A HEATING MEANS SUPPLYING HEAT TO A DEVICE WHOSE TEMPERATURE IS TO BE CONTROLLED AND MAINTAINED; AN ELECTRICAL SWITCH MEANS COUPLING SAID HEATING MEANS TO SAID SOURCE OF POTENTIAL FOR SELECTIVELY APPLYING SAID POTENTIAL TO SAID HEATING MEANS TO CAUSE IT TO APPLY HEAT TO SAID DEVICE IN RESPONSE TO CONTROL SIGNALS; A TEMPERATURE SENSING MEANS FOR CONTINUOUSLY PROVIDING A FIRST CONTROL POTENTIAL PROPORTIONAL TO THE ACTUAL TEMPERATURE OF SAID DEVICE; AND ADJUSTABLE SOURCE OF REFERENCE POTENTIAL FOR PROVIDING A SECOND CONTROL POTENTIAL PROPORTIONAL TO A PRESELECTED DESIRED TEMPERATURE LEVEL AT WHICH SAID DEVICE IS TO BE MAINTAINED; AND AN ELECTRICAL COMPARISON AND CONTROL MEANS COUPLED TO SAID TEMPERATURE SENSING MEANS AND TO SAID ADJUSTABLE SOURCE OF REFERENCE POTENTIAL FOR RECEIVING AND COMPARING SAID FIRST AND SECOND CONTROL POTENTIALS AND PRODUCING CONTROL SIGNALS IN RESPONSE THERETO, SAID ELECTRICAL COMPARISON AND CONTROL MEANS INCLUDING A TUNNEL DIODE COUPLED TO A UNIJUNCTION TRANSISTOR AND SAID ELECTRICAL SWITCHING MEANS COMPRISING A CONTROLLED RECTIFIER TRIGGERED BY A UNIJUNCTION TRANSISTOR WHICH IS COUPLED TO SAID ELECTRICAL COMPARISON AND CONTROL MEANS FOR CAUSING SAID SOURCE OF POTENTIAL TO BE SELECTIVELY APPLIED TO SAID HEATING MENS IN ACCORDANCE WITH SAID CONTROL SIGNALS TO MAINTAIN SAID DEVICE AT SAID PRESELECTED DESIRED TEMPERATURE LEVEL.