Patent GB-933771-A (GB)
Title: Remote transmission of measurement values
IPC: H03M1/00
Filed: 1959-11-30
Abstract: 933,771. Electric selective signalling systems. SIEMENS & HALSKE A.G. Nov. 30, 1959 [Nov. 28, 1958], No. 40549/59. Class 40 (1). Apparatus for transmitting instrument indications over a distance comprises a rotary scanning member carrying a lug which cooperates with a stationary highfrequency generator to generate a starting pulse which causes a pulse transmitter, driven in synchronism with the rotary member, to be connected with a distancetransmission circuit, and a second high-frequency generator moving with the rotary member and cooperating with a lug associated with the pointer of an instrument so as to generate a stopping pulse which disconnects the pulse transmitter from the distance-transmission circuit. As described, repeated readings of a liquid-level meter having a scale 1 graduated 0-1000 millimetres and a further scale 20 graduated 0-50 metres are transmitted to a remote receiver. Scanning discs 5 and 15, a pulse-generating disc 25, are driven by a pneumatic motor and geared together so as to rotate at speeds-disc 25: disc 15: disc 5 :: 200: 10: 1. Devices 9, 6, 16 and 29 are H.F. oscillators which cease to oscillate when lugs or plates 7, 3, 19, 26, 27 pass between their scan coils 8, 4, 16, 28. Oscillator 9 is stationary and sends a " start " pulse to a scaleof-three counter 31 when the lug 7 on the slowest disc 5 moves between its coils 8. When a flipflop 32 of the counter 31 comes " on " it switches a flip-flop 22 which, via a gate 39, opens a gate 38 and allows pulses equivalent to the passage of short and long lugs 27, 26 demodulated by a device 30, to pass to a transmitter 37. When the coils 17 of oscillator 16 reach plate 19 on the pointer 18 of the 0-50 metre scale, a " stop " pulse switches back the flip-flop 22 and cuts off the supply of pulses to the transmitter by closing gates 38, 39. Subsequently, when the next " start " pulse is generated by the oscillator 9, the flip-flop 33 of counter 31 is energized and this switches over a flip-flop 13 to allow pulses from the generator 25 and demodulator 30 to pass to the transmitter 37 until the coils 4 of oscillator 6 reach plate 3 on the pointer 2 of the 0-1000 mm. scale, thus generating a " stop pulse which switches back the flip-flop 13. The third state of counter 31 allows time for operations at the receiver end to be completed before the reading out cycle is repeated. Transformers 10 and 21, each of which may comprise two pot-shaped cores open at one end and mutually opposed, not only supply LF current from a generator 11 to the moving oscillators 6 and 16, but also serve to pass the H.F. signals back to suitable filters and demodulators 12, 12a. At the receiving end, Fig. 3, the signals arriving at terminal 40 are tested in a device 41, an interference indicator 42 being activated if the signals are not valid, and then passed to counters 43, 44 in parallel. If the counts do not agree a signal is passed by a comparator 46 to the indicator 42. Moreover, if counter 43 becomes overloaded a device 47 responds and signals the indicator 42; The first set of pulses counted, representing the metre value, is passed into a " coarse " store 48, and the reading of the mm. scale passes to a " fine " store 49. By means not described, the two values are checked against each other and the metre value increased or decreased by one, if necessary, e.g. when the metre reading lies in a region such as 5.999 to 6.000 metres. The indicating device 51 may be supplemented by a graphic device, e.g. fine stylus, strip-printer &c.