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A safety circuit for deenergizing an electric blanket of the type utilizing a positive coefficient resistance material as the heating element positioned between a pair of spaced conductor wires. The circuit includes one or more gas tubes with parallel resistances connected across the conductor wires

A safety circuit for deenergizing an electric blanket of the type utilizing a positive coefficient resistance material as the heating element positioned between a pair of spaced conductor wires. The circuit includes one or more gas tubes with parallel resistances connected across the conductor wires to sense voltage changes caused by open or short circuits and to conduct sufficiently high currents to blow a series connected fuse.

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In an electrical circuit, the combination comprising a heating cable including a pair of spaced conductors separated throughout their lengths by a layer of positive temperature coefficient resistance material, each of said conductors having a power supply end and a sensing end, a power supply cord c

In an electrical circuit, the combination comprising a heating cable including a pair of spaced conductors separated throughout their lengths by a layer of positive temperature coefficient resistance material, each of said conductors having a power supply end and a sensing end, a power supply cord connected to said cable at said power supply ends of said conductors to connect said cable to an alternating current power supply, a current responsive switching means in series with one of said conductors, a sensing means connected to said sensing ends of said conductors, said sensing means including a pair of series connected impedance elements, a pair of gas tube elements connected in series between said power supply ends of said conductors, the junction of said impedance elements and the gas tube elements being connected together, said gas tube elements being nonconducting under normal operating conditions and conducting when shorts or open circuit conditions occur in said conductors, said gas tube elements having sufficient current capacity in the conducting state to activate said switching means in series with said cable.