Abstract: A rotary speed measurement device includes an oscillator including a resonant circuit with a coil which conducts a resonant current to develop a magnetic field therearound. A wheel is connected to rotate together with a rotating member and is provided along circumference with alternately arranged first and second marks which causes different magnetic effect on the magnetic field. The coil is disposed adjacent the wheel so as to sense the magnetic effect and provide a corresponding voltage Vs. An analyzer is provided to give a parameter Vsub based upon voltage Vs and to compare the parameter with a predetermined threshold V.sub.TH to give a pulse when the parameter exceeds the threshold as indicative of that the wheel rotates by an increment corresponding to an angular distance between the first mark and the adjacent second mark. The pulse is counted by a counter within a unit time to obtain a rotary speed of the wheel.

Abstract: A switching system for selectively distributing a laser beam from a laser source to one of a plurality of welding stations for laser welding thereat. The system includes a first optical fiber directing the laser beam therethrough, and a pair of second optical fibers leading to the welding stations, respectively. A switching device connects the first optical fiber selectively to one of the second optical fibers so as to pass the laser beam to the corresponding welding station for enabling the laser welding thereat. The switching device comprises a housing having a longitudinal axis and holding input ends of the second optical fibers in parallel relation with the longitudinal axis, a carrier supporting an output end of the first optical fiber and linearly movable together therewith within the housing in a direction perpendicular to the longitudinal axis such that the output end of the first optical fiber comes into and out of closely end-to-end facing relation to the input ends of the second optical fibers.

Abstract: A miniaturized electromagnet has an enhanced armature attraction force and reliable armature movement. The electromagnet comprises an L-shaped flat magnetic plate of magnetic material with a horizontally extending core and a first yoke leg depending from one end of the core. An excitation coil is wound around the core. A second yoke member is formed separately from the magnetic plate into a plate configuration and is coupled secured at its upper end to the other end of the core so as to depend therefrom in an opposed relation to the first yoke leg. The lower end portion of the second yoke leg is bent toward the first yoke leg to define thereat a pole plate extending parallel with the core.

Abstract: A.C. switching circuit capable of opening and closing contacts without generating any arc. When D.C. source restores from its interruption, the contacts are maintained in or shifted to a predetermined state. A change-over switch is provided for selecting as required whether the contacts are to be forcibly opened or closed after the D.C. source interruption, or whether the previous state of the contacts is to be maintained.

Abstract: Circuit arrangements for the control of a bistable relay having a capacitor connected in series with the relay coil. The series connection of the coil and the capacitor is connected to an excitation voltage for actuating the relay and simultaneous charging of the capacitor. When the excitation voltage is removed, the series connection is short-circuited through a semiconductor switch, whereby the capacitor is discharged and the relay switched back to its initial position. The bistable relay is thus operated as monostable relay.