586,170. Telemetering. HAZELTINE CORPORATION. Aug. 14, 1944, No. 15504. Convention date, Aug. 24, 1943. [Class 40 (i)] In a system for indicating the readings of a plurality of meters, electrical signals representative of the indications of each meter are produced by scanning means and synchronizing signals of a different type and meter-reference signals, having a different electrical characteristic to distinguish them from the previous signals, are produced by means operating synchronously with the scanning device, all the signals being combined for transmission. The scanning means 10, Fig. 1, for each meter 12 comprises a motor-driven rotor 13 carrying coils 17 tuned by a condenser 19 in series with the rotor winding 20, the stator winding 22 being connected to the input of an oscillator 23. The meter pointer 11 carries a strip of high-resistivity, highpermeability material which at each revolution alters the impedance of the tuned circuit and generates a negative signal. The signals from the various instruments are applied in succession by a distributer 44, which rotates at a slower speed than the scanners, to a mixer 43. A similar-scanning device comprising a rotating pointer 35 scans a fixed tuned coil 37 and controls an oscillator 40 to produce signals which are differentiated in a network 421 to feed to the mixer negative reference signals for each meter and positive synchronizing signals. The scanning device is phased so that these signals are produced when the distributer arm 45 is contacting insulating segments 53, 54, 55. When the arm 45 engages segments 46, 50 an oscillator 27 is keyed into operation by a network 26 to generate negative meter-reference signals of a higher repetition rate than the previous signals. Curve A, Fig. 3, shows the output from the mixer 43 comprising meter indication signals 61, 62, reference signals 60, 601, 6011, synchronizing signals 64, 641, 6411 and meter reference signals 63. At the receiver, Fig. 2, the positive signals pass through a separator 67 and the negative signals through a separator 73, both sets being reversed (Curves B, C). The output from 73 is integrated (Curve D) and then differentiated (Curve E) in a network 74 and applied to a multi-vibrator 75 in which the negative pulse extinguishes tube 76 and fires 77, this condition being reversed by the next synchronizing pulse 641 from 67, thus producing a broad pulse (Curve F). This after differentiation at 79 (Curve G) controls a second multi-vibrator 80 to produce a second broad pulse (Curve H) which is terminated by the next synchronizing pulse 6411 - and is flattened (Curve I) by a limiter 81. The output from the separator 73 is superimposed in a mixer 82 and the wave-form shown in curve J is applied to the control electrode 83 of the cathode-ray tube 65. The output from 80 also controls a third multi-vibrator 801 to produce a similar broad pulse on which the output from 73 is superimposed to give the wave-form shown in curve N for controlling the cathoderay tube 66. The synchronizing signals from 67 cause the beams to trace a circle in synchronism with the scanning at the transmitter, and the tubes are biassed to be non-conductive except for signals of large amplitude; so that spots are produced by the reference signals and by the meter indication signals of the corresponding instrument.
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