GB1198993A - Improvements in or relating to the Remote Control and Monitoring of Apparatus - Google Patents

Abstract

1,198,993. Vehicle control signals. ELECTRIC & MUSICAL INDUSTRIES Ltd. 27 Oct., 1967 [29 Oct., 1966], No. 48654/66. Heading B7N. A vehicle, e.g. crane 1, on rails 2 is driven by motor 3 from a 3-phase A.C. supply picked up by brushes 9, 10, 11 from bus-bars 6, 7, 8 and controlled and monitored from a control station 38 by signals at supply frequency transmitted via bus-bars 20, 21, 22 and brushes 23, 24, 25 and having a phase relation with the A.C. supply which is a function of the information transmitted. The 3-phase supply is applied to a Scott Transformer 30 at the control station which supplied real (0 degree) and quadrature (90 degrees) signals on lines 35, 36 to transmit units 40, 41 and receive unit 42. Each transmit unit, e.g. 40 includes a pair of modulators 50, 60 each supplied with one of the signals. The real phase signal is applied to auto transformer 51 in modulator 50 so that gates 52, 53, 54, only one of which can be opened at a time, can select one of three taps on the transformer giving zero signal or phase displaced signals of 0 degrees and 180 degrees. Similarly modulator 60 can select zero signal or phase-displaced signals of + 90 degrees and - 90 degrees. Switch unit 63 by opening one gate in each modulator can thus signal one of nine conditions, the two signals being combined by transformers 61, 62 and passed via bus-bar 20 and brush 23 to the crane. Transmit unit 41 is similar except that each modulator is separately controlled by a switch 65, 66 giving two separate control signals each selecting one of three conditions. The signals are combined and applied via bus-bar 21 and brush 24 to the crane. Each picked-up signal is applied to a demodulator 70, 71 each, e.g. 70 including a pair of phase-sensitive detectors 72, 73. A real phase reference signal obtained from Scott Transformer 74 on the crane, is applied to one detector and a quadrature reference signal to the other and the output signal +V, 0 or -V from each detector is applied to decoding apparatus 77 on the crane. In a similar manner signals monitoring various conditions on the crane are transmitted by transmitter unit 80 on the crane to receiver 42 at the Central Station. The conductive connection between transmitter and receiver may be replaced by a transmission system using radio, light or sound waves or inductive or capacitive signalling.