Abstract: A reactor core includes a plurality of laminations of trapezoidal shape forming the legs of the core. These legs are arranged in generally rectangular configuration with air gaps provided at the corners of the core. These air gaps extend diagonally of the core legs and are formed between the inclined faces of adjacent ends of the trapezoidal-shaped core legs. End plates each having a longitudinal section extending parallel to and fixed to one of the legs and having flanges at each end of the longitudinal section extending perpendicularly to the longitudinal section are provided for maintaining the legs of the core in assembled relation and for effecting adjustment of the air gaps. The end plates include elongated openings in the flanges thereof for permitting movement of each of the end plates, and the leg to which it is affixed, relative to the remainder of the core for varying the size of the diagonal air gaps.

Abstract: A variable inductor wherein two closed magnetic circuits each having a predetermined gap in one place are constructed of a movable magnetic core and a fixed magnetic core. When the movable magnetic core is moved, the opposite area between both the magnetic cores in one of the closed magnetic circuits increases, while the opposite area between both the magnetic cores in the other closed magnetic circuit decreases. Thus, the inductances of coils wound around parts of the respective closed magnetic circuits vary complementarily.

Abstract: A transducer for converting mechanical forces into corresponding electrical signals. In one embodiment, the transducer takes the form of a writing instrument for use in a user identification system whereby the time-varying force between the instrument and a writing surface generates a waveform which is characteristic of the individual doing the writing. The transducer includes first and second core members being interconnected by a resilient member with the core members being operatively coupled to a coil whose inductance varies in accordance with the forces generated during writing. The coil is operatively coupled to an oscillator whose frequency changes in accordance with the varying inductance to produce the waveform.

Abstract: An electrical inductance coil, having a central opening therethrough, is surrounded by a spaced shield of magnetic metal, and a screw of magnetic metal is mounted in engagement with one side of the shield for adjustable extension through the central opening in the coil for varying the spacing between the inner end of the screw and the confronting, opposite side of the shield.