Abstract: The transformer ensures the transmission of electrical power by electromagnetic induction between the first (11) and second (12) coils concentrically arranged on the first (7) and second (8) tubular parts respectively, which are made of a ferromagnetic material, and coaxially mounted in such a way that an outer surface (13a, 13b, 13c) of one part can rotate in relation to an inner surface (14a, 14b, 14c) of the other. These surfaces each consist of two straight cylindrical rotation surfaces (13a, 13c; 14a, 14c) of different diameters, each extending from one of the axial ends of the part (7; 8) to an intermediate radial shoulder (13b, 14b) for connecting these surfaces. The parts (7; 8) are arranged head-to-foot one inside the other so as to delimit, between the shoulders (13b; 14b), an annular space receiving the coils (11, 12), between two annular gaps each delimited by two (13a, 14a; 13b, 14b) of the facing cylindrical surfaces of the first (7) and second (8) parts.

Abstract: A low cost x-y digitising system is described for use in consumer electronic devices, such as portable digital assistants, mobile telephones, web browsers and the like. The digitizer includes a resonant stylus, an excitation winding for energising the resonant stylus and a set of sensor windings for sensing the signal generated by the stylus, from which the x-y position of the stylus is determined. The excitation signals applied to the excitation winding are designed to reduce the power drawn from the power supply which makes the digitising system particularly suited to battery operation.

Abstract: Processing circuitry is provided for processing signals received from, for example, sense coils forming part of a position encoder used to encode the relative positions of two relatively moveable members. The position encoder is such that each of the plurality of signals from the sense coils varies sinusoidally with the relative position of the members but out of phase with respect to each other. The processing circuitry comprises mixers for multiplying each of the received signals with one of a corresponding plurality of periodic time varying signals, each having the same predetermined period and a different predetermined phase, and an adder for adding the signals from the mixers. The phase of the mixing signals are chosen so that the output signals from the adder contains a single periodic component having the predetermined period whose phase varies with the relative position of the two members.

Abstract: An a-c current sensor for measuring the current which flows in a conductor has an insulating frame having a central compartment open at its upper end and encompassed by a U-shaped receptacle for a bent portion of the conductor. A coil is housed in the central compartment. The frame is slidingly mounted within a sleeve made of a soft magnetic material and having two assembled half-shells. The voltage generated by the current across the coil is proportional to the intensity of current flow.