the improved heating pad includes a flexible , thin film heating element with two independent semiconductor circuits printed on an electrically insulating surface , laminated between overlying and underlying organic polyester sheets , and electrically connected to an external power source , wherein the heating element is hermetically sealed in an outer organic polymer covering . thermostats are positioned directly over the semiconductive circuit traces . the circuit traces are connected in parallel by a multi - position switch , with each circuit capable of being energized separately or in combination , and each circuit capable of providing heat over the entire area of the pad . a circuit protective device provides a varistor across the power supply and a fast - acting fuse in series with the circuit traces .