US2974197A - Synchronizing arrangement for a regenerative telegraphic repeater utilizing signal transitions - Google Patents

Synchronizing arrangement for a regenerative telegraphic repeater utilizing signal transitions Download PDF

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Publication number
US2974197A
US2974197A US471422A US47142254A US2974197A US 2974197 A US2974197 A US 2974197A US 471422 A US471422 A US 471422A US 47142254 A US47142254 A US 47142254A US 2974197 A US2974197 A US 2974197A
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switch
gate
time scale
milliseconds
condition
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US471422A
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English (en)
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Wright Esmond Philip Goodwin
Terry Victor John
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International Standard Electric Corp
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International Standard Electric Corp
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L7/00—Arrangements for synchronising receiver with transmitter
    • H04L7/02—Speed or phase control by the received code signals, the signals containing no special synchronisation information
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L7/00—Arrangements for synchronising receiver with transmitter
    • H04L7/02—Speed or phase control by the received code signals, the signals containing no special synchronisation information
    • H04L7/033—Speed or phase control by the received code signals, the signals containing no special synchronisation information using the transitions of the received signal to control the phase of the synchronising-signal-generating means, e.g. using a phase-locked loop
    • H04L7/0331—Speed or phase control by the received code signals, the signals containing no special synchronisation information using the transitions of the received signal to control the phase of the synchronising-signal-generating means, e.g. using a phase-locked loop with a digital phase-locked loop [PLL] processing binary samples, e.g. add/subtract logic for correction of receiver clock

Definitions

  • an electronic regenerative repeater for start-stop printing telegraph signals sent at regular intervals comprising a non-continuously running time base for timing the regeneration operation and means for starting the time base at different positions in accordance with differences in time of arrival of a start element.
  • start-stop signal combinations With start-stop signal combinations the time occupied by the start and stop elements is wasted as regards conveying intelligence and it is therefore common to send telegraph signals over radio channels by synchronised systems, that is, systems in which the time scale circuits at transmitter and receiver are continuously running and are kept in synchronism by separate synchronising signals. It is a very simple technical matter to arrange synchronous operation by means of a separate signalling channel but such an arrangement is not economical, particularly on long radio channels.
  • system check elements for checking the accuracy of the elements of a signal combination are transmitted in addition to the signal elements and the system is such that signal combinations received from a teleprinter are re-transmitted over a synchronous channel and therefore without start and stop elements.
  • the combinations transmitted over the synchronous channel are seven element combinations made up by adding to the intelligence carrying elements of each combination received from the teleprinter two check elements. These check elements are added at the end of the other combinations.
  • Fig. 1 shows the time scale circuit, and the circuits for starting, stopping and correcting the positions of said time scale.
  • Fig. 2 shows a circuit for determining what corrections are to be applied to keep the time scale in synchronism with that at a transmitter.
  • FIGS. 1-10 are functional diagrams each symbol used standing for a device performing a particular function, the physical nature of the device and its manner of performing the function being well known.
  • the reference characters for the various symbols have been allotted in such a manner as to denote the nature of the device and also the figure of the drawings upon which each appears.
  • each reference character consists of a numeral followed by a letter.
  • counting circuits are denoted by the letter C and the various counting circuits are distinguished by the preceding numeral.
  • the first digit of the numeral indicates the figure upon which the symbol denoted by the reference character appears.
  • Gate circuits are denoted by the letter G; gate circuits 101G to 114G appear on Fig. 1 and gate circuits 201G to 2146 on Fig. 2.
  • Multi position switches are denoted by the letter F, the difierent positions of these switches being denoted by rectangles within which diiferent numerals or letters appear. In the case of two position switches the letters denoting the positions have some relation to the functions performed by the switches in the respective positions.
  • a two position switch such as 11F with positions ST and SP can take the form of two cold cathode gas filled tubes interconnected so that when one is made conducting the other becomes non-conducting.
  • This output conductor is shown as a line adjacent only to the device or devices to which such potential is applied and the reference character applied to the line is the same reference character as the position which gives the potential output but with the letters in the lower case.
  • an output from the tube ST of 11F is denoted 11 st.
  • 11C denotes a counting circuit which may take the form of that shown and described in U.S. Patent 2,787,657, issued April 2, 1957 and may control the application of potentials to various other circuits at various times in the time scale of counting.
  • This counting circuit counts pulses from a source of pulses. Negative pulses from this source appearing on the lead marked P are applied, as will be explained later, to the counting circuit and cause successive elements of a chain of static electric switches (in the example referred to cold cathode electric discharge gaps) to be placed in conducting condition.
  • the pulses recur at a frequency of 500 kc./s. and thus successive elements are made conducting at intervals of 0.2 millisecond.
  • the cycle of the counting circuit is 145 milliseconds. Only certain elements in the counting circuit are indicated, viz. those operated at times 0, 98, 102 and 144.8 milliseconds from the time of the pulse that operates the first element 0.
  • the first five elements of a recived signal combination occupy 100 milliseconds and when transmission first commences a signal combination of five marks followed by two spaces is received as explained above.
  • the transition from mark to space therefore occurs nominally at 100 milliseconds in a time scale of which Zero represents the commencement of the first signal element.
  • the counting circuit is therefore set to commence initially in the neighborhood of 100 milliseconds in its time scale. The drawing shows conditions for setting it at this time at 102 milliseconds.
  • the incoming signals received over the radio channel are detected and applied to a demodulator which causes pulses from the same source as that supplying -P to appear on one or other of two conductors marked M and S respectively in Figs. 1 and 2 according as the incoming signal condition is mark or space, as described in US. Patent 2,787,657.
  • Conductor S provides one input to a gate 101G, another input being provided by the element 1 of a two position switch 12F.
  • Switch 12F is normally in the position in which element 1 thereof is conducting.
  • gate 101G When therefore the incoming signal condition changes to spacing, gate 101G is opened (it requires two input conditions to open it as denoted by the numeral 2 inside the circle) and presents one input condition to gate 105G which also requires two input conditions to open it.
  • the other condition is supplied by switch 11F in its normal condition of element SP conducting.
  • Gate 105G is therefore opened and element ST of switch 11F made conducting, element SP becoming non-conducting.
  • the switch 11F provides a momentary pulse on the lead marked 11 whenever it changes over from one condition to the other. This pulse is applied over gate 102G to set (or reset) counter 11C in position 102 milliseconds from zero of the time scale, the switch 23F being in position 4 and supplying a second input gate 102G.
  • the switch 23F is normally reset to position 4 as will be clear from a later part of the description.
  • the counting circuit 11C applies potentials to one input to a gate 104G at 105 milliseconds, i.e. 3 milliseconds after starting up, and at five milliseconds thereafter up to zero in the time scale.
  • Another input is supplied by a switch 12F when in its normal position 1 and a third input by the mark conductor 1N1.
  • gate 104G is opened and passes forward a condition to open gate 11GG and give a step to counter 12C.
  • Counter 12C has three positions so that marking conditions found at two consecutive times of examination drive this counter to position 2. In this position gate 108G is opened, followed by the opening of gate 107G and the restoration of switch 11F to position SP.
  • the application of pulses to the time scale ceases, as gate 103G is no longer opened, and the momentary pulse on 11ft advances the counting circuit 11C to position 102 and resets counter 12C to position 0.
  • the spacing condition should persist for 45 milliseconds (the last element being assumed to last for 25 milliseconds) as described in the said British Patent No. 771,301.
  • the channel may be subject to interference which will cause a marking condition to appear during this 45 milliseconds and a true start may be rejected because of this interference.
  • the counting circuit 11C will be set in operation on one of these repetitions. In fact seven such repetitions will occur per second and if the start cannot be made effective the channel is unlikely to be fit for transmission.
  • the counter 11C which provides a time scale for controlling the operations of the receiver and regenerator is stepped by a source of pulses of the same frequency as that stepping a similar counting circuit which provides a time scale for controlling the operations at the transmitting end of the channel.
  • the invention provides a correcting device which corrects the movement of the time scale at the receiver to compensate for any apparent loss of synchronism in a manner which is similar to that used in the said US. Patent 2,749,386 for correcting for early or late arrival of a start element in start-stop reception.
  • the mark and space leads M and S from the demodulator above referred to are connected to the respective elements M and S of a two position switch 21F, so that during a marking condition element M is operated, during a spacing condition element S is operated. At each change-over a pulse is produced on conductor 21ft.
  • a second two-position switch 22F is placed in position E by potentials applied from the counting circuit 11C at 10, 30, 50, 70, 110 and 130 milliseconds from zero on the time scale and placed in position L by potentials applied from the counting circuit 11C at times corresponding to normal transition times viz 0, 20, 40, 60, and 120 milliseconds (the time of milliseconds is omitted for reasons which will appear later).
  • a multi-position switch 23F is reset into its middle position 4 by output 11c from counting circuit each time the scale reaches 105. It will be seen that switch 22F in position E denotes an early transition and in position L a late transition. This is used to drive switch 23F towards a higher position for each late transition and towards a lower position for each early transition.
  • switch 23F With switch 23F in position 4 and switch 22F in position L, potentials are applied from 23 4 and 22f1 to a gate 201G which is opened to apply an input to a gate 202G. If now in this condition a signal transition occurs, a pulse applied over 21 to gate 202G passes through the gate and operates switch 23F to position 5.
  • gate 205G is opened to drive switch 23F into position 7.
  • gate 208G is opened and applies an input to gate 209G.
  • a pulse occurs on 21ft it passes through gate 209G and drives switch 23F to position 2.
  • the switch 23F If the switch 23F has been driven in one direction or the other by late or early transitions and a transition of the other kind occurs, it is driven in the reverse direction. This is subject to the exception that it is not driven into position 4 from either position 3 or back from position 5, though similar gating arrangements could be applied to do this if thought necessary.
  • switch 23F If, however, switch 23F has been driven into position 2 by two successive early transitions it is driven to position 3 it the next transition is late. This is done by opening of gate 2116 when switch 23F is in position 2 and switch 22F in position L. The opening of gate 2116 applies an input to gate 207G so that an impulse on 21ft due to transition of switch 21F drives switch 23F to position 3.
  • switch 23F If switch 23F has been driven into position 6 by two late transitions, an early transition drives it back to position 5 by means of gates 2136 and 202G, whilst an early transition when switch 23F is in position 7 drives it back to position 6 by means of gates 2146 and 2046.
  • each transition from mark to space starts counter 11C from 102 milliseconds 1n its cycle as described above.
  • switch 12F is driven into position 2.
  • counter 12C is given a step by application of potentials over gate 115G to open that gate, followed by the opening of gate 116G.
  • Counter 12C is thus stepped into position 1.
  • potential applied from the counter 11C at 100 milliseconds in the cycle to gate 106G opens that gate, which causes opening of gate 1076 to cause element SP of switch 11F to be operated.
  • switch 11F is unaffected when the counter reaches 100 milliseconds immediately thereafter, because the initial switch-over of switch 11F causes output 11ft to restore counter 12C; to position 0 and thus gate 106G will not be opened at 100 milliseconds.
  • any lack of synchronism between the time scale circuit at the transmitter and the time scale circuit 11C is corrected periodically by reseting time scale circuit 11C forward or back from the position reached.
  • time scale 110 can be varied by resetting it to different positions less than 100 milliseconds according to the number of early transitions i.e. according as 23F is in position 3, 2 or 1 and to different positions beyond 100 milliseconds according as 23F is in position 4, 5, 6, or 7.
  • the time scale circuit 11C could be initially started at the 100 millisecond position and reset to that position if switch 23F remains in position 4.
  • time at which switch 22F is changed over may be varied so that transitions are disregarded unless they occur within a small margin, say 3 milliseconds, either side of the nominal change-over time.
  • the receiving equipment can come to rest when transmission terminates. This condition can be recognised by the fact that a certain maximum number of characters arrive with elements entirely marks.
  • the switch 13F is restored to position M at time 0 on the time scale of 11C.
  • a gate 1116 the condition of the switch 21F and thereby the condition of the incoming signals is examined at times 10, 30, 50, 70, 90, 110 and milliseconds in the time scale of 11C, i.e. one for each signal element and if a space is being received at any of these times switch 13F is driven to position S. If no space has been received so that switch 13F remains in position M, inputs are supplied to a gate 11126 at milliseconds in the time scale 11C to allow a pulse from a source of pulses P through the gate to step the counter 13C one step.
  • the ten point counter 13C having positions 0 9 is stepped once for each character consisting wholly of marks. If nine such characters are received in succession, counter 13C reaches position 9, "but these must be nine consecutive characters, since each time switch 13F goes into positions S since its output 13 3 restores counter 13C to zero position over gate 113G.
  • Counter 13C in position 9 drives switch 12F into position 1. Also in this position a potential is applied from 13c9 over gate 1086 and a second input is supplied from 1271. Gate 108G is opened, followed by the opening of gate 1076 and switch 11F is driven to position SP. With switch 11F in this position and counter 13C in position 9 a gate 1146 is opened and potentials applied over gate 113G to restore co under 13C to position 0.
  • the receiving circuits then await the receiving channel going to space before restarting operations.

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  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Monitoring And Testing Of Exchanges (AREA)
  • Meter Arrangements (AREA)
  • Measurement Of Unknown Time Intervals (AREA)
US471422A 1953-12-10 1954-11-26 Synchronizing arrangement for a regenerative telegraphic repeater utilizing signal transitions Expired - Lifetime US2974197A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB34416/53A GB771302A (en) 1953-12-10 1953-12-10 Improvements in or relating to communication channels conveying information in the form of a code

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US2974197A true US2974197A (en) 1961-03-07

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Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2527638A (en) * 1947-09-26 1950-10-31 Bell Telephone Labor Inc Pulse skip synchronization of pulse transmission systems
US2749386A (en) * 1952-02-08 1956-06-05 Int Standard Electric Corp Telegraph repeaters
US2752425A (en) * 1948-06-14 1956-06-26 British Telecomm Res Ltd Regenerative repeater
US2816163A (en) * 1949-12-14 1957-12-10 Nat Res Dev Synchronizing system for signal receivers
US2822422A (en) * 1953-08-17 1958-02-04 Int Standard Electric Corp Start-stop telegraph regenerators

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2527638A (en) * 1947-09-26 1950-10-31 Bell Telephone Labor Inc Pulse skip synchronization of pulse transmission systems
US2752425A (en) * 1948-06-14 1956-06-26 British Telecomm Res Ltd Regenerative repeater
US2816163A (en) * 1949-12-14 1957-12-10 Nat Res Dev Synchronizing system for signal receivers
US2749386A (en) * 1952-02-08 1956-06-05 Int Standard Electric Corp Telegraph repeaters
US2822422A (en) * 1953-08-17 1958-02-04 Int Standard Electric Corp Start-stop telegraph regenerators

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BE534007A (en))
NL95598C (en))
GB771302A (en) 1957-03-27

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