A device and method for generating heat employs a heating element which is resiliently compressible or in which the electrical resistance can otherwise be varied, for a given electric current, to vary the level of heat generated. In a specific embodiment the device employs a plurality of layers of electrically...http://www.google.es/patents/US6107612?utm_source=gb-gplus-sharePatente US6107612 - Heating device and method
