Abstract: In an apparatus and method for preventing instability of a stepper motor operated by a plurality of alternating currents of different respective phases and controlled by a sequence of control pulses, the control pulses defining an angular parameter of the stepper motor, the steps include determining the sum of the phase currents, transforming the sum of the phase currents into a voltage fluctuating about an average value, determining the average voltage, and thereafter feeding back the fluctuating voltage so as to angle-modulate said control pulses.

Abstract: Circuitry for measuring the torque of a stepping motor is disclosed. The circuitry is based on the fact that the decay time of the current flowing through the stator coils is a function of the torque of the stepping motor.

Abstract: A simple mechanical counting device is disclosed. The counting device includes a simple zero reset mechanism which enables the counter to be easily reset to zero by the use of a finger of the human hand.

Abstract: A multipole key switch comprises switching chambers disposed next to each other are each provided with a movable contact bridge, which shortens a pair of contact fingers in each case in the turned on condition. Contact supports for supporting the contact bridges are formed at a cross-web of an actuating arm. Each switching chamber is provided with a restoring spring. The force of only two restoring springs can bring the key switch into its switched-off position. In order to prevent a sideways canting or clamping of the actuating ram, it is provided with two ribs, with the aid of which it is guided in a guide track.

Abstract: A rotational restriction lock is formed as a one-piece restricting element which is resiliently mounted on a rotor shaft and has a hub which is always resiliently driven in rotation by the rotor throughout a small angle, spring arms which transmit the rotary movement, and movable rotation restricting elements to which the rotary movement is transmitted and the ends of which prevent the rotor from rotation in an undesired direction, but allow the rotation of the rotor in a desired direction. Adjustable abutments are provided for selecting a permissible angle of rotation of the hub.

Abstract: A document is disclosed, which contains information invisible to the naked eye, but which information can be made visible by a simple method. Said information is represented by markings on the document, which markings comprise a first color at least partially opaque to at least part of the invisible light spectrum, and a second color which serves to conceal said first color in the visible spectrum, but which second color is itself transparent to said part of the invisible light spectrum.

Abstract: Two identical toggle springs of a snap action switch are inserted in the same knife-edged bearings and are spaced apart in the region of their clamping locations and are activated by the same plunger. There are two control arms connected to the toggle springs each having a movable contact. The relative distance between the control arms is limited by a lost motion buffer. Stationary contacts are positioned above and below the movable contacts. The control arms are actuated by the plunger and move in the same direction as the plunger establishing contact between one of the movable contacts of the control arms and one of the stationary contacts.

Abstract: A miniature electric motor having substantially identical stator halves which are connected together by lugs axially interengaging on the circumference of the stator.The lugs of the stator halves resiliently engage in pairs on a common plane between ribs formed on a plastics material ring which is located inside the stator halves and which also forms an outer protective casing for the coils and the rotor parts of the motor. The lugs may be slotted at their free ends to provide resilient shanks.

Abstract: A miniature synchronous motor having a bell-shaped rotor and a damping body, freely mounted, but non-rotatable on the rotor shaft. The damping body being urged, at least substantially in a radial direction by a spring, the force of which also acts substantially equally for both bearings of the motor so as to reduce noise during operation.