Patent GB-659007-A (GB)
Title: Method and devices for position transmitting by means of time modulated electric pulses
IPC: G08C19/24
Filed: 1949-03-02
Abstract: 659,007. Electric selective signalling. GLOESS, P. F. M. March 2, 1949, No. 5682. Convention date, March 12, 1948. [Class 40 (i)] [Also in Group XL (c)] In a telemetering or like system the meter pointer or other moving element sweeps over a delay line to which short-recurrent electric pulses are fed. A reference pulse is fed to the transmission line as each generated pulse commences its travel along the delay line and is followed by a line pulse picked up capacitatively or inductively from the delay line by a member movable with the pointer. This pulse is thus time-modulated in accordance with the meter reading. The reference pulses may be supplied to several series-connected delay lines associated with separate meters, the respective time - modulated line pulses serving to operate a single cathode-ray tube receiver indicator. Variables such as temperature and liquid level may actuate the transmitter directly. Transmission. As shown, the pointers of instruments 25-29, Fig. 3, sweep over respective series-connected delay lines 31-32 ... terminating in the characteristic impedance 33. An oscillator 30 feeds short recurrent pulses to these delay lines over a further delay line 38. Capacitative couplings 39 produce in the collector line 34 a three-pip synchronizing pulse as each generated pulse commences its passage along the delay line 38, and similar couplings 18, 19 produce two-pip reference pulses in line 34 as the generated pulses commence their passage through the respective delay lines 31, 32 .... Further line pulses are produced by capacitative coupling elements 2 on the respective meter pointers as the generated pulses pass thereby along the delay line, these line pulses being timemodulated in accordance with the reading of the associated pointers. The line pulses are passed through an amplifier selector stage 52, which removes parasitic pulses, to a radio transmitter 53. Reception, Fig. 5. The received signals are demodulated at 61, the triple-pip synchronizing signals are separated at 62 and fed to a scanning generator 63 which produces the slow vertical sweep of the beam of a C.R.T. 71. The two-pip reference pulses are separated at 66 and fed to a scanning generator 67 producing the horizontal deflection of the C.R.T. beam so that a number of horizontal time bases appear one for each meter 25-29. The time modulated pulses applied to the control grid produce bright spots 72, 73 ... 76 on the respective traces corresponding in position to the respective meter readings. Alternatively, the time-modulated pulses may be connected to supplementary deflecting-plates to produce a blip in the horizontal beam trace. The C.R.T. screen may be covered by an opaque mask, Fig. 6 (not shown), with scaled slots for each horizontal trace. Transmitter construction. The pointer 1, Figs. 1, 1a, carries a vane 2 of metal or high permettivity dielectric material, e.g. titantium dioxide, which moves between a concentric electrode 3 and the delay line consisting of a coil 5 wound on a former 6 having a longitudinallyextending conducting band 7, e.g. sprayed thereon, the wire and strip forming the two conductors of the delay line. The electrode 3 which acts as collecting electrode for both reference pulses and the time-modulated pulses preferably increases in width from left to right to compensate the attenuating effect of the delay line and maintain constant the amplitude of the line signals. This may be achieved, alternatively, by using an electrode 3 of constant width which gradually approaches the delay line 2 from left to right. Modifications. The reference pulses may be distinguished from the time-modulated pulses by their length, polarity, amplitude, or composition, and may be directly supplied by the oscillator 30, Fig. 3. For measuring temperature, Fig. 7, a metallic or dielectric float 83 on the thermometer liquid 84 is moved between a delay line 85 and a parallel electrode 86 and functions in the same manner as the vane 2 of Fig. 1. The delay line may be wound on the thermometer tube, Fig. 8 (not shown), the line time modulated pulse being produced by reflection of the travelling pulse at the liquid surface and collection of the reflected pulse at the line input. The same principle may be used for measuring liquid level, Figs. 9, 10 (not shown). The telemetering pulses may be combined with television pulses, being transmitted during the return movements of the line scanning. Where the system is used on aircraft the pulse generator may be on the ground and its output transmitted to the aircraft by radio, in which case the system may be combined with a radio altimeter. The modulator of Figs. 1, 1a may be used in a radio range detector in which a luminous spot is adjusted over the C.R.T.. range indicator screen until it coincides with the echo spot by adjustment of the modulator, this adjustment being indicative of the range.