Abstract: A contact-free push-button key for converting mechanical energy into an electrical signal has a toroidal tape core comprised of material having a low magnetic retentivity such as an amorphous metal alloy, the toroidal tape core having an electrical winding thereabout and being deformable upon actuation of a key button thereby inducing a voltage change in the associated winding as a result of the changing magnetic characteristics during deformation. The deformable toroidal core is contained in a housing covered by a slidable push-button key which deforms the core when pressed.

Abstract: An amorphous alloy core is converted into a crystalline state at least at one zone along the core body and such zone extends at least over a portion of the core cross-section at such zone. The zone converted into the crystalline state functions as an air gap of prior art crystalline low-retentivity alloy cores, because the permeability in the crystalline state is significantly lower than in the amorphous state. Magnetic cores formed in accordance with the principles of the invention are suitable in applications wherever a sheared hysteresis loop is required.