GB553286A - Improvements in or relating to remote indication systems - Google Patents

Abstract

553,286. Position-indicating systems. STANDARD TELEPHONES & CABLES, Ltd. (International Standard Electric Corporation). March 13, 1942, No. 3376. [Class 40 (i)] [Also in Group XL] The angular position of a shaft, such as a switch shaft, is remotely indicated by shifting the phase of a reference A.C. and producing therefrom a train of pulses, one per cycle, which are used in conjunction with the reference wave to give an indication on a cathode ray tube or other low inertia device. Indications in respect of a number of shafts may be transmitted with the help of distributers ; summation may be effected by subjecting the reference A.C. to successive phase shifts corresponding to the positions of several shafts. The conversion of the phase-shifted A.C. into impulses may be performed at the transmitter or receiver. Phase shift is effected by supplying the reference A.C. in quadrature to a pair of fixed coils intersecting at right angles, output being taken from a coil rotatable about the axis of intersection and positioned by the shaft. The frequency should be high enough to permit the use of air-cored coils but a low reference and pulse frequency may be used by modulating a higher frequency for phase shifting, followed immediately by rectification. Such an arrangement is shown in Fig. 6 in which low reference frequency in quadrature from 14 and high frequency in quadrature from 15 are supplied to a, twin modulator 16 which feeds the phaseshifter 13 controlled by shaft 12. The phaseshifter output is rectified at 17 and supplied to a pulse generator 8 producing one pulse per cycle, the pulses and the reference wave from 14 being used to modulate a wireless transmitter 19. A monitoring cathode ray oscillograph may be connected to leads 21-23. At the receiver, Fig. 7, the detector 25 is followed by high and low pass filters 26, 27 which separate the pulses from the reference wave and apply both to the control circuit 9 of a cathode ray tube 10. In a multiplex system, Figs. 8 and 9 (not shown),the phase-shifters for several shafts are supplied by common devices corresponding to 14-16, Fig. 6 and their outputs are fed over a rotary distributor to common devices corresponding to 17, 8 and 19. The distributer is driven by a motor supplied with the reference wave and also controls a square pulse generator which interrupts the radiated wave once per revolution for giving synchronizing indications at the receiving distributer the motor of which is also supplied with the reference wave. A number of shaft position indications could be given on a single cathode ray tube.