Temperature sensitive control wires provided with transistors for electrically heated pads, blankets and the like

Claim 1

AN ELECTRONICALLY CONTROLLD ELECTRICALLY HEATED BLANKET OPERABLE FROM A MAINS VOLTAGE SOURCE COMPRISING A HEATING ELEMENT ADAPTED TO BE OPERATED AT MAINS VOLTAGE, A HEAT SENSOR COMPRISING A PAIR OF WIRES POSITIONED IN CLOSE PROXIMITY TO ONE ANOTHER THROUGHOUT THEIR LENGTH; A HEAT SENSITIVE ELECTRICAL CONDUCTOR OF RELATIVELY HIGH ELECTRICAL RESISTANCE AT NORMAL ROOM TEMPERTURES IN COMPARISON WITH THE RESISTANCE OF SAID WIRES EMBEDDING THE WIRES, AND OF NEGATIVE CO-EFFICIENT OF ELECTRICAL RESISTANCE, THE HEAT SENSOR BEING SUBSTANTIALLY THE SAME LENGTH AS, AND LOCATED AT LEAST IN CLOSE PROXIMITY TO THE HEATING ELEMENT THROUGHOUT ITS LENGTH, A RELAY HAVING CONTACTS WHICH ARE IN CIRCUIT WITH THE HEATING ELEMENT, A SOURCE OF D.C. POTENTIAL OF APPROXIMATELY 22 VOLTS; AND A TRANSISTOR AMPLIFIER THE INPUT OF WHICH IS CONNECTED TO THE PAIR OF WIRES AND THE SOURCE OF D.C. POTENTIAL AND THE OUTPUT OF WHICH IS CONNECTED TO THE RELAY, THE CIRCUIT CONNECTED TO THE D.C. SOURCE BEING ELECTRICALLY ISOLATED FROM THE CIRCUIT OF THE HEATING ELEMENT.