US2361593A - Transmission regulation - Google Patents

Transmission regulation Download PDF

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Publication number
US2361593A
US2361593A US467947A US46794742A US2361593A US 2361593 A US2361593 A US 2361593A US 467947 A US467947 A US 467947A US 46794742 A US46794742 A US 46794742A US 2361593 A US2361593 A US 2361593A
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US
United States
Prior art keywords
repeaters
transmission
repeater
amplifier
pilot
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
US467947A
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English (en)
Inventor
Harold S Black
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
AT&T Corp
Original Assignee
Bell Telephone Laboratories Inc
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority to NL133662D priority Critical patent/NL133662B/xx
Priority to NL72713D priority patent/NL72713C/xx
Priority to BE473974D priority patent/BE473974A/xx
Application filed by Bell Telephone Laboratories Inc filed Critical Bell Telephone Laboratories Inc
Priority to US467947A priority patent/US2361593A/en
Application granted granted Critical
Publication of US2361593A publication Critical patent/US2361593A/en
Priority to FR947817D priority patent/FR947817A/fr
Priority to GB16342/47A priority patent/GB624923A/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B3/00—Line transmission systems
    • H04B3/02—Details
    • H04B3/04—Control of transmission; Equalising
    • H04B3/10—Control of transmission; Equalising by pilot signal
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B3/00—Line transmission systems
    • H04B3/02—Details
    • H04B3/04—Control of transmission; Equalising
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B3/00—Line transmission systems
    • H04B3/02—Details
    • H04B3/04—Control of transmission; Equalising
    • H04B3/06—Control of transmission; Equalising by the transmitted signal

Definitions

  • This invention relates to electric wave transmission systems and more particularly to automatic regulation of the transmission characteristics throughout a long distance signaling system comprising many repeaters.
  • the invention has for one of its principal ob- J'ects a reduction in the effect of the transient response that appears in repeatered transmission systems having dynamic regulation of repeater gain.
  • Another and related object is to enable a substantial increasein the number of dynamically regulated repeaters that may be used in tandem in 'a transmission system, and therefore also to enable an increase in the length of the system,
  • each delivers the sig- 112.15 and pilot wave to the next transmission section in their original condition, i. e., the condition of constant average total power.
  • the transmitted effect that controls 'the gain adjustment at each repeater is, except at the first one, an effect that is simultaneously operated upon also by the gain regulator at each preceding repeater.
  • the repeater next following the origin of the change eventually completely compensates for it by proper adjustment of its gain, but inasmuch as any change in the control effect is communicated instantly to all of the other following repeaters, the gain regulators associated with the latter immediately attempt to effect a compensating change in the gain of their respectively associated repeaters.
  • the net result is that even in the normal operation of thesystem a change in the controleifect at any point not only calls into proper action the repeater regulator next following that point but also gives rise to a transient operation of the regulators at all of the other following repeaters.
  • One object of the' invention is to enable such systems to be substantially extended without incurring an excessive transient effect.
  • a plurality of different kinds of regulators are employed in a system for the dynamic contro1 of the transmission characteristics of repeaters, the different kinds of regulators differing in respect of the rate at which they respond to a given change in the control effect that is supplied to them, and the relative number and spacing of each kind of regulator is systematically allocated in such manner as to substantially reduce the effect of transients or alternatively to permit substantial increase in the length of the system over which dynamic regulation can be successfully maintained.
  • the invention contemplates the division of a repeatered transmission system into a plurality of sections with transmission regulators at the junctions thereof, and progressive subdivision of the sections with transmission regulators of progressively slower rates of response interposed at the junctions resulting from each subdivision.
  • the invention contemplates a repeatered transmission system comprising a plurality of sections eachembracing dynamically regulated repeaters in such limited number, in relation to the rate of response of the regulators, as to preclude the development of an excessive transient wholly within the section, and dynamic repeater regulators at the junction of sections each having a rate of response fast enough to substantially suppress the transmission, from the preceding section to the next one, of such transient effects as may develop within the preceding section.
  • the invention contemplates further the interposition of one or more additional dynamically regulated repeaters haying a faster rate of response calculated to substantially suppress any transient which the succession of fast-acting regulators would of itself make possible in a long system.
  • Fig. 1 shows schematically a multiplex carrier telephone system embodying the invention
  • Figs. 2 and 3 illustrate schematically circuit details thereof.
  • Fig. 1 there is represented schematically a repeatered wire line transmission system which it may be assumed for specific example is adapted for multiplex carrier telephone transmission. Although a, single one-way system is illustrated it will be understood that it would be paired with an oppositely-directed system for two-way telephone transmission.
  • terminal circuits l' translate the telephone signals received over the several exchange circuits to respective positions in the carrier frequency range. For specific example, there may be twelve voice frequency circults and twelve respectively corresponding carrier frequency channels ranging in frequency from somewhat more than twelve to somewhat less than sixty kilocycles.
  • the translated signals from the terminal circuit are applied, together with pilot waves f1, f2 and f3, to the input of an amplifier 2.
  • the latter is arranged to supply pilot waves f4 which are so automatically varied in intensity that the average total wave power delivered by amplifier 2 to the transmission line 3 is maintained substantially constant.
  • Repeaters 4 are of a constant output type, to be described further with reference to Fig. 2, and they may be spaced in the line 3 at the usual frequent intervals of fifteen miles, for example, in the case of a cable circuit.
  • Repeaters 5 are of a type artemperature.
  • each repeater is designed ,to compensate for the loss-frequency characteristic which the preceding section of transmission line has at some predetermined line
  • Each also introduces a variable amount of gain, uniform over the frequency range of interest, to compensate approximately for changes in line attenuation induced by changes in temperature.
  • Repeater 5 additionally compensates for such changes in transmission equivalent of the system as are non-uniform with respect to frequency.
  • terminal amplifier 2 this may be of the type disclosed in United States patent to C. O. Mallinckrodt, No. 2,231,542, dated February 11, 1942, or in the application of J. O. Edson, Serial No. 467,945, filed of even date herewith. In either case it may be described as a stabilized negative feedback amplifier having constant and uniform gain for waves applied to its input terminals, and as a generator of pilot oscillations of frequency ii. In either case too the intensity of the generated oscillations is varied by a current-dependent thermosensitive resist-;
  • the oscillation intensity may range from almost zero to a value comparable with the maximum anticipated signal intensity. Under certain conditions the power input to amplifier 2 may be so great. that the oscillation intensity may reduce to zero and yetnotprevent a substantial increase in the total power output of the amplifier. This fact is important inasmuch as the effect described may give rise to a transient operation of the regulator.
  • Each repeater 4 comprises an amplifier of type such that the total wave power output thereof remains substantially constant despite variation of the wave power input to the amplifier over a wide range.
  • Th amplifier may take the form shown in my United States Patent No. 2,209,955, dated August 6, 1940, or in J. H. Bollman Patent No. 2,231,558, dated February 11,
  • the amplifier is essentially a stabilized negative feedback amplifier having in the negative feedback path a current-dependent thermosensitive resistance 1 which. operates to vary the gain of the amplifier to compensate for any tendency of the wave power output to vary from a predetermined value.
  • the repeater amplifier 4 that is illustrated schematically in Fig. 2 comprises an input transformer I0 and four associated impedance branches designed inaccordance with the teachings of H. W. Bode application, Serial No. 435,171, filed March 18, 1942, and issued as Patent No. 2,337,965, datedDecember 28, 1943, to provide a fixed amount of equalization calculated to compensate for the attenuation-frequency characteristic of the preceding transmission line section at an assumed normal line. temperature. Connectionof the' input network to the input termi v livered to the outgoing line through an output transformer H which is arranged in the'manner described in E. H. Perkins Patent No. 2,210,001,
  • Thermistor I Interposed in series in the feedback connection 7 I4 is the current-dependent thermosensitive resistance l and associated impedance elements which together control the amount of loss in the negative feedback path.
  • Thermistor I has a negative temperature coefficient of resistance and it is so proportioned that its temperature and resistance are controlled by the feedback currents traversing it in accordance with the average power content thereof.
  • the circuit elements can be and are so proportioned that the resistance of thermistor 1 and the over-all gain of the amplifier may vary over a wide range while the total wave power output varies over a minute range. Thus if the wave power input to the amplifier should increase, for example, because of some change in line condition, the output of the amplifier would tend to increase in proportion. Any increase in the power output, however, increases the flow of current through thermistor 1, reduces the resistance of the thermistor and increases the amount of negative feedback, thus reducing the gain of the amplifier and allowing only a slight net increase in the total wave power output.
  • thermistor I upon a change in the wave power input to the amplifier, thermistor I cannot instantly assume the proper temperature and resistance called for by the changed condition, for a finite time is-required to heat the thermistor to a higher temperature and a finite time is likewise required for it to cool to a lower temperature.
  • a thermistor such as T can be designed in manner well known in the art to have any predetermined rates of response to an increase or decrease, respectively, in the intensity of the current traversing it.
  • the thermal time constants of thermistor 7 then control the rate of response of the gain regulators at repeaters 4.
  • Thermistor 6 in terminal amplifier 2 likewise has finite thermal time constants, hence the total wave power delivered to the line 3 is constant only as averaged over some small but finite time interval.
  • the development of transients in'the operation of the regulators and the suppression of such transients both involve the electrothermal properties of the thermistors 6 and l.
  • the signals received from the terminal circuits I may all be fairly strong.
  • the total wave power is, for a short time at least, of such intensity that even though the pilot oscillations f4 are reduced to zero, the total power delivered to the line 3 exceeds the predetermined constant value.
  • powerful pulses of ringing or ring-back current may appear in one or more of the voice frequencycircuits and their corresponding carrier channels with the same temporary eiTect on the power output of the amplifier 2.
  • pulses of, excess power are of short duration. and usually less than one second, their energy content may be sufficient to call the regulators at the repeaters 4 into action.
  • thermistor 6 must first cool sufficiently to allow oscillationsto resume and cool further to allow the oscillation intensity to build up to the required value.
  • the circumstances described are not the only ones which can give rise to undesirable transient effects, for lightning strokes on.the line, for example, can have the same effect on repeater regulators of the kind described.
  • the thermistors l in the regulated repeaters 4 are designed to be extremely sluggish; they may have, for specific example, a thermal time constant of the order of forty-five seconds for heating and one hundred thirty seconds for cooling.
  • the thermal time constant indicates the time elapsing after a change in heating power delivered to the'thermistor before the resulting correction in thermistor resistance and repeater gain is approximately two-thirds completed.
  • the input power at any of the repeaters 5 will vary as the attenuation of the preceding section of line varies, and it will vary also in accordance with any transients developed within the preceding string of repeaters 4 and any other fluctuations in transmission equivalent too rapid to be compensated by the preceding repeater regula-
  • the loss-frequency characteristic of each network is controlled in a manner known in the art by a respective thermistor 23, 25, 25. whichis'indirectly heated under the control of a respective pilot wave, f1, f2, is.
  • Network 20 determines theamount'of fiat gain. It introduces a lossthat is uniform over the twelve to sixy-kilocycl ire quency range, and the amount of loss is controlled by pilot ii.
  • the pilot f1 which may have a frequency of fifty-six kilocycles for specific example, is partially diverted at the output of each repeater 5 througha filter F1 and appliedto a control one cuit 26f
  • the latter supplies heating current to the heater associated with thermistor 23 and the' By virtue of intensity of the heating current is continually varied in correlation with the variations in the intensity of the pilot wave f1 appearing at the output of the repeater.
  • the circuit elements are so proportioned and arranged that any departure in the output intensity of the pilot f1 from a predetermined normal value gives rise to a compensating change in the gain of the repeater amplifier such as to maintain the pilot intensity at substantially its normal value.
  • thermistor 23 and control circuit 26 are designed to respond to a given change in pilot intensity at a rate much faster than the rate at which repeater 4 would respond to the same change in total power output. If the control circuit 26 is made fast enough in its operation, the speed of the flat gain regulator comprising thermistor 23 will be substantially dependent on the thermal time constants of the latter. In such case suitable time constants for thermistor 23 are 0.2 second. I will be noted that this is at least two hundred times that of thermistor I and represents a different order ofmagnitude.
  • any repeater 5 takes place rapidly enough to substantially suppress the transmission of such variations as the repeaters 4 fail to compensate, and more especially the rate of response is fast enough to compensate for, and substantially prevent the transmission of, any transient effects developing within the preceding string of repeaters 4.
  • the repeatered transmission system is in a sense divided into substantially isolated sections in so far as the transient operation of the regulators 4 is concerned, and at the same time dynamic regulation is maintained over the entire system.
  • Networks 2! and 22 and their respectivelyassociated thermistors 24 and 25 operate under the control of the transmitted pilot f2 and fa, respectively, tocompensate for changes in transmission equivalent that are not uniform with respect to frequency. These changes may be regarded as comprising a change in the slope of the transmission-frequency characteristic and a change in the curvature of the characteristic. Assuming that network 2
  • the former are made comparatively sluggish in their operation.
  • Their thermal time constants may be, for example, sixty seconds average for heating and cooling cycle.
  • Strong power pulses applied to the 1nput of a repeater 4 of the form shown in Fig. 2 may reduce the feedback loss to such an extent that oscillations are generated within the amplifier at a frequency or frequencies above or below the twelve to sixty-kilocycle band. This condition may be prevented from persisting after the power pulse has ceased, by designing the feedback circuit, and more especially theoutput transformer l3 to attenuate transmission between the output of the amplifier and the thermistorv I at the critical frequency or frequencies.
  • pilot-controlled transmission regulators between the pairs of successive sections, said pilotcontrolled regulators being many times faster in their regulating action than said constant output repeaters.
  • a long distance repeatered signaling system comprising a transmission line subject to variations inattenuation, means at a multiplicity of repeater points automatically regulating repeater gain under the control of currents transmitted through said line, the speed of response of said'regulating means to a change in the said control currents being great enough to follow variations in the attenuation of said line, means at a plurality of less frequent repeater points automatically regulating repeater gain under the control of currents transmitted through the line, the speed of response of said last-mentioned means to a change in the said currents controlling it being many times as great as the said speed of response of said first-mentioned regulating means.
  • the two said regulating means difiering from each other in respect of the rate at which they respond to a change in the respectively corresponding control effect.
  • the method of automatic transmission regulation which comprises effecting relatively low speed dynamic regulation at a multiplicity of points in each of a pluralit of successive sections of said system, and efiecting relatively high speed dynamic regulation at each of the junctions of said sections, whereby transients tending to develop as a result of the operation of the said low speed regulation in any one section are substantially prevented from afiecting the low speed regulation in following sections.
  • a long distance transmission system subject to variations in attenuation, a multiplicity of repeaters spaced apart in said system, means at certain of said repeaters for automatically regulating the gain thereof under the control of an effect transmitted through the system, said regulating means operating relatively slowly, means at less frequent repeaters for automatically regulating the gain thereof under the control of another effect transmitted through the system, said second-mentioned regulating means operating relatively quickly, and each of said regulating means substantially compensating for said variations in attenuation.

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  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Cable Transmission Systems, Equalization Of Radio And Reduction Of Echo (AREA)
  • Control Of Amplification And Gain Control (AREA)
US467947A 1942-12-05 1942-12-05 Transmission regulation Expired - Lifetime US2361593A (en)

Priority Applications (6)

Application Number Priority Date Filing Date Title
NL133662D NL133662B (xx) 1942-12-05
NL72713D NL72713C (xx) 1942-12-05
BE473974D BE473974A (xx) 1942-12-05
US467947A US2361593A (en) 1942-12-05 1942-12-05 Transmission regulation
FR947817D FR947817A (fr) 1942-12-05 1947-06-11 Régulation de transmission
GB16342/47A GB624923A (en) 1942-12-05 1947-06-20 Improvements in or relating to signal transmission systems

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US467947A US2361593A (en) 1942-12-05 1942-12-05 Transmission regulation

Publications (1)

Publication Number Publication Date
US2361593A true US2361593A (en) 1944-10-31

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US467947A Expired - Lifetime US2361593A (en) 1942-12-05 1942-12-05 Transmission regulation

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US (1) US2361593A (xx)
BE (1) BE473974A (xx)
FR (1) FR947817A (xx)
GB (1) GB624923A (xx)
NL (2) NL133662B (xx)

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3105942A (en) * 1958-12-12 1963-10-01 Philips Corp Automatic gain control amplifier system
US3355670A (en) * 1964-03-10 1967-11-28 James J Pastoriza High-speed switching apparatus
US3525048A (en) * 1968-02-01 1970-08-18 Foxboro Co Process instrumentation system with dynamic compensator

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3105942A (en) * 1958-12-12 1963-10-01 Philips Corp Automatic gain control amplifier system
US3355670A (en) * 1964-03-10 1967-11-28 James J Pastoriza High-speed switching apparatus
US3525048A (en) * 1968-02-01 1970-08-18 Foxboro Co Process instrumentation system with dynamic compensator

Also Published As

Publication number Publication date
BE473974A (xx)
NL133662B (xx)
NL72713C (xx)
GB624923A (en) 1949-06-17
FR947817A (fr) 1949-07-13

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