Patent GB-686829-A (GB)
Title: Improvements in or relating to electronic scanning systems
Inventor: DUNN ROLAND HARRIS
IPC: H04Q9/04
Filed: 1949-05-31
Abstract: 686,829. Electric signalling systems. STANDARD TELEPHONES & CABLES, Ltd. May 31, 1950 [May 31, 1949], No. 14591/49. Class 40 (i). In a remote supervisory system, a plurality of objects located at a remote point and capable of a plurality of discrete conditions, are continuously and cyclically scanned, and their condition indicated at a central station under the control of the scanning means. Two embodiments are described both using synchronous electronic distributers at the central and the remote point. In one embodiment where the objects are grouped at a plurality of substations, connected partyline fashion, three communication channels are used, one for sending selective combinations of five unit " mark "-" space " code signals for selecting the substations in turn, a second for synchronizing and distributer control signals and a third for sending back indication signals to the central station. In the second embodiment, one transmission line only is used between the central station and one substation only, indication signals being sent in both directions interleaved with synchronizing and distributer signals. First embodiment, schematic, Fig. 1. Four substations 19, 19<SP>1</SP>, 19<SP>11</SP>, 19<SP>111</SP> are shown connected over lines 8, 9, 10 to the main station where a pulse, generator 1 supplies basic pulses to which the system is synchronized. A controller 2 divides the pulses into cycles of pulses 13 with a resetting and distributer pulse 14, distinguishable e.g. by its polarity, amplitude or duration, for stepping a distributer 3 at the end of each cycle. All pulses 13, 14 are applied over line 10 to all substations in parallel. In the successive positions of the distributer, respective coders 4, 4<SP>1</SP>, 4<SP>11</SP>, 4<SP>111</SP> are energized to produce predetermined combinations of positive (mark) and negative (space) pulses synchronized with the basic pulses. These code pulses are sent over line 8 to all substations where only the decoder 20-20<SP>111</SP> appropriate to the selected station responds. At this station the scanner 21 is energized and scans the objects 22 one by one in step with the received pulses 13, being stopped and reset by pulse'14 which also clears down the decoder. As each object is scanned, a pulse is generated characteristic of its condition, these indication pulses being routed by the operative sender 23 ... 23<SP>111</SP> over line 9 to all the receivers 5.. 5<SP>111</SP> at the main station. These receivers are energized one at a time in step with the associated coders 4 ... 4<SP>111</SP> so that the appropriate receiver only is effective. It is stepped by the pulses 13 from the controller in synchronism with the pulses from the substation which are routed to associated elements in the corresponding display 6 ... 6<SP>111</SP> to indicate the positions of the scanned objects. In this way the substations are scanned in turn. Figs. 2, 3, 4 show the first embodiment in more detail. Fig. 2 shows the main station common equipment, and Fig. 3 the main station equipment provided in respect of the respective substations. Fig. 4 shows the equipment of any one substation. The controller comprises a control train 24 and a pulse train 25, each of which consists of a cold cathode tube counting train. The control train consists of a number of tubes equal to one in excess of the number of scanning steps per group and counts continuously in successive cycles when pulsed from the pulse generator 1. The tubes of the pulse train fire only if pulses from the pulse generator arrive when the tubes are biased by the output pulses from the corresponding tubes in the control train so that the pulse train output is synchronized with the pulse generator. Once per cycle, over line 28. the control train pulses the distributer 3 which also consists of a gas tube counting train, Fig. 14 (not shown). The tubes of the distributer are biased in common and fire in turn on coincidence of this bias with a pulse from the generator 1 over lead 29, the tubes being arranged so that as a tube fires, it primes the next and extinguishes the previous tube. The output of the pulse train 25 is fed over lead 32 to the pulse line sender 31. these pulses corresponding to pulses 13. Fig 1. The reset pulse corresponding to 14 Fig. 1, is passed from the distributer at each step thereof over lead 30. In the pulse line sender, Fig. 13 (not shown) the pulses 13, 14 are converted into "mark" and " space " pulses of shorter duration and fed to the control channel 10 which reverts to earth potential between pulses. As each tube of the distributer fires it energizes, over an individual lead in cable 33, the corresponding coder 35 ... 35<SP>111</SP> Fig. 3. The coders, Fig. 15 (not shown) comprise a train of five gas discharge tubes fed in common with pulses from the last five tubes of the control train over cable 36. Only that coder energized from the distributer operates corresponding to the substation to be scanned in the following cycle. The coder train tubes fire in turn and each has two outlets corresponding respectively to "mark" and "space". The outlets are connected so as to produce a selective combination of five marks and/or spaces which are fed over line 37 to the code line sender 38. This unit is similar to the pulse line sender Fig. 13 (not shown) where the code pulses are shortened before transmission over the selecting channel 8. Substation operation, Fig. 4. The five unit code sent over the selection channel, and the control pulses 13, 14 over the control channel, pass to respective receivers 39, 45 at all substations. These units, Fig. 16 (not shown) are similar and serve to deliver output pulses corresponding in time to the leading edge of the corresponding channel signals with the exception of the reset pulse which is delivered with trailing edge timing. Each code receiver passes the " mark " and " space " signals over leads 40, 41 to a decoder- 42, Fig. 17 (not shown) which is a six tube counting train of which the last five tubes are connected for pulse supply to one or other of the leads 40, 41 according to the pattern to which the coder is required to respond. Only in the coder corresponding to the selected substation will all five tubes fire, to feed an output pulse to energize the associated pilot train 44. The pilot train, Fig. 17 (not shown), is also a counting train of which the first tube is triggered by the pulse from the decoder after which the tubes are fired in turn by the pulses 13 over line 47. Individual outputs from the pilot train tubes are connected to respective objects to be scanned e.g. relay contacts at 49. which according to their position divert the pulses to a " red " or "green" indication train 50, 51. These are also gas tube trains Fig. 17 (not shown), arranged so that those tubes fire which receive a pulse from the line receiver 45 simultaneously with one from the pilot train by way of the associated scanned objects. During a cycle, therefore, each scanned object on being reached, fires the corresponding tube in either the " red " or " green " indication train. At the end of the cycle the reset pulse over lead 46 clears down the operative pilot train and indication trains, as well as the decoders at all substations. The individual indication tubes in the trains 50, 51 which are fired send pulses to the indication line sender 54, Fig. 18 (not shown) which is started and stopped in synchronism with the pilot train 44 by "start" and "stop" signals therefrom, and converts the "red" and "green" indication pulses into " mark " and " space " signals for transmission over the indication channel 9 to the line receiver 57 at the main station, Fig. 2. The line receiver 57, Fig. 19 (not shown) passes both " mark " and " space indication pulses to a check train 60, Fig. 20 (not shown) which counts the total pulses in a cycle and prevents an indication in the event of an error in the count. The " mark " indication pulses only are also fed in common to the marker trains 61 ... 61<SP>111</SP>, Fig. 21 (not shown). These trains are also gas tube trains similar to 50, 51. Only that train operates which receives an initial signal from the distributer over'cable 34. The tubes of the operative marker train are biased in turn from the control train 24 over cable 26 or this could be done by the check train. Coincidence of bias over cable 26 and an indication "mark " pulse over lead 59, fires the ,corresponding tube in the marker train and a corresponding relay of the associated marker relays 62 ... 62<SP>111</SP> operates when a tube fires. At the end of the cycle, therefore, marker relays will have been operated corresponding to " mark indication pulses from the operative substation. A check pulse now arrives from the check train, providing its count is correct, and energizes the operated contacts of all the marker relays to actuate the associated lamps or other indicating means 63 ... 63<SP>111</SP>. " Space " indication pulses are not passed to the display markers as the marker relays are normally in the position corresponding thereto. The display remains until just before the corresponding substation is to be scanned but the check train is cleared down at the end of each cycle. In this way the substations are scanned in turn to set their associated displays 63 ... 63<SP>111</SP> at the main station, the lamps flickering according to the scanning speed. Second embodiment, Figs. 5, 6. In this case, ten indications are transmitted to the main station, Fig. 6, and two indications sent back to the substation, Fig. 5. Free running oscillation generators 65, 165 are used at the sub and main stations, respectively, which are synchronized alternately from opposite ends of the single transmission channel 73. At the substation, the generator 65 pulses a control train 68 consisting of a gas tube counting train of sixteen tubes. The output of the first