US2426222A - Electrical communication system - Google Patents

Electrical communication system Download PDF

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Publication number
US2426222A
US2426222A US475687A US47568743A US2426222A US 2426222 A US2426222 A US 2426222A US 475687 A US475687 A US 475687A US 47568743 A US47568743 A US 47568743A US 2426222 A US2426222 A US 2426222A
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United States
Prior art keywords
signals
telephone
telegraph
signal
band
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Expired - Lifetime
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US475687A
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English (en)
Inventor
Katchatouroff Leon
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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
    • H04M—TELEPHONIC COMMUNICATION
    • H04M11/00—Telephonic communication systems specially adapted for combination with other electrical systems
    • H04M11/06—Simultaneous speech and data transmission, e.g. telegraphic transmission over the same conductors
    • H04M11/062—Simultaneous speech and data transmission, e.g. telegraphic transmission over the same conductors using different frequency bands for speech and other data
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04M—TELEPHONIC COMMUNICATION
    • H04M11/00—Telephonic communication systems specially adapted for combination with other electrical systems
    • H04M11/06—Simultaneous speech and data transmission, e.g. telegraphic transmission over the same conductors

Definitions

  • the present invention relates to electric communication systems in general, and has reference in particular to systems in which telephone and telegraph signals are transmitted over the same line.
  • the invention relates to systerns in which. currents of telephonic frequency are used for telegraph signals or the like, whereby at least one telephone conversation and one telegraph communication can take place simultaneously.
  • telegraph signals as used herein is intended to cover not only telegraph signals, in the strict sense of the word, but also remote control signals, voice frequency calls and any other signalling, either by telegraphy or telephony or other methods of signal transmission independent of the latter two.
  • the general object of the present invention is to improve the operation of transmission systems of the above-mentioned type and assure gocd transmission of telegraph and telephone signals over existing telephone circuits that may be of inferior quality and particularly those that have a low upper cut-off frequency.
  • Fig. 1a shows frequency attenuation curves ob tained from an existing transmission system of the above-mentioned type
  • Fig. 1b shows frequency attenuation curves for a system of the same type as in Fig. 1a, but incorporating the improved features of the present invention
  • Fig. 2 illustrates diagrammatically and in simplified form an embodiment of a receiver am plifier circuit for tele-printers constructed in the usual manner
  • Figs. 3a and 31 show examples of signals cle formed by passage through narrow band filters applied to the circuit of Fig. 2;
  • Fig. 4 shows examples of the shapes of signals, amplified by the circuit according to Fig. 2, which act upon the motor relay of the tele-printer re-' DCving apparatus after transmission over a variable attenuation line equipped with narrow band filters;
  • Fig. 5 shows diagrammatically an example of a simplified amplifier receiving circuit for a teleprinter incorporating the features of the invention
  • Fig. 6 shows examples of the shapes of signals
  • the frequency band allotted to telegraphic communications is usually placed above the frequency band reserved for telephony.
  • the telephony frequency band A (Fig. 1a) is limited upwardly at 1700 P. P, S. While the frequency band for telegraphy ranges from 1950 to approximatel 2250 P. P. 6., as indicated by the letter B in Fig. la; the telegraphic communications contemplated in this instance being tele-printer communications.
  • the Cut-off frequency is set, as a matter of practice, below 2200?. P. S, in such cases, the telegraph channel presents, aside from any questions of impedance irregularities, a prohibitive attenuation, and operation of the telegraph system is rendered impossible.
  • An object of the present invention is to provide means which will overcome these disadvantages.
  • the band for telegraphy is placed in a position where the conditions for transmission over the telephone line are more certain, namely, right within the telephonic frequency band.
  • a band is first of all eliminated from the telephonic transmission range of the system and this eliminated band is then utilized for telegraphic transmission.
  • it sufiices to place the telegraphic band in any desired spot of the band, between 500 and 1800 P. P. S. of the telephone frequencies which, it should be noted, will insure good transmission over any kind of telephone circuit.
  • the present invention fixes the carrier current of the telegraphic communication in the center of the usual telephone frequency band of 500 to 2500 P. P. S., i. e., at 1500 P. P. S.
  • the frequencies transmitted over the telephonic range run from 300 to 1250 P. P. S. (band C of Fig. 1b) and from 1750 P. P. S. up to the cut-01f frequency of the lines used (band E, Fig. 1b).
  • the band D which transmits superimposed telegraph communications, has a value of about 300 P. P. S. and the separation obtained between the two channels amounts to 60 db.
  • Such high value of the band of 300 P. P. S. which is lost for telephony, may be reduced, however, to 200 P. P. S., if desired, by using intermediate telegraph relays.
  • the present invention accomplishes this result by means of an automatic adjusting device disposed in the receiver amplifier of the tele-printing installation.
  • This adjusting device consists of means for diminishing the amplification of the first stages by means of la. supplemental negative polarization created at the moment when the signal is received.
  • the circuit, wherein this polarization is created, is so arranged that polarization continues not only during the length of the signal proper, but also during the passage of the signal drag.
  • This adjusting device is particularly eiTective when the telephone line is traversed by no current and the so-called working condition of the line is the one that corresponds to a transmission of current at voice frequency.
  • this adjusting device With the aid of this adjusting device, it is possible to assure not only operation of the system when the attenuation of the line circuit varies frequently, but also easy starting of the apparatus. In other words, with this device it is always possible to obtain a connection of medium quality by setting the two control attenuators at zero. Moreover, control reception is possible even if the mechanism especially used for this purpose is not properly adjusted.
  • Fig. 2 illustrates diagrammatically a simplified embodiment of a circuit for a tele-printer without automatic adjustment.
  • the incoming signals traverse attenuator I and are transmitted by transformers 2, 3 to grid 1 5 of first amplifier tube l.
  • This first amplifier stage 4 is connected to a second amplifier-detector stage 5.
  • the output of the amplifierdetector stage 5 is connected to the control grid of the direct current amplifier tube 6
  • Whose plate circuit includes relay 7 of the tele-printer motor of the receiving station.
  • this plate current has a predetermined value for example 24 mA.
  • the motor relay 1 of the teleprinting receiver which is inserted in the plate circuit of last mentioned tube 6, is actuated.
  • the plate current will remain zero during a period of time substantially equal to the period of time 15 corresponding to the length of the signal proper.
  • a parasitic drag amplitude is created after the signal as a result of the passage of the same across the narrow band filters. This parasitic drag amplitude, which has a lower value than to, is insufficient to reduce the plate current and hence incapable of actuating the relay.
  • duration separated by intervals of the same duration, are transmitted from a distant point across a telephone line equipped with narrow band filters.
  • the attenuation of the line is 30 db. (attenuators such as element I of the receiver and transmitter being eliminated)
  • the received signals are virtually undeformed.
  • the attenuation of the circuit is reduced, the received signals become stronger and stronger, the distortion of the duration increases and becomes practically prohibitive, while the printing apparatus is rendered inoperative.
  • the negative polarization in question is created automatically by the received signal itself.
  • the voice frequency tension taken off the plate circuit of the first tube 4 is applied simultaneously to the control grid 8 of the triode D tion of tube 5 and to plate 9 of one of the diodes of this tube (which remains unused, or is not provided at all, in the circuit according to Fig. 2).
  • a rectifier circuit is inserted between this diode and the ground It.
  • This rectifier circuit includes the dry rectifier H, for instance of the copper oxide type, the condenser I2 and resistances l3 and Hi.
  • a portion of the direct current of the diode traverses the rectifier H and charges condenser l2.
  • the rectifier is connected so as to be traversed. by the charging current in direction of its lowest resistance.
  • the values of the condenser lZ, of the resistance of rectifier H in the aforementioned direction and of the resistances is and M are so adjusted that the charging time of condenser I2 is of milli-second magnitude.
  • This reduction is the greater, the highcr'the value of the negative supplemental polarization is, i. e., the higher the value of the strength of the received signal is.
  • the present invention provides for auto-polarization of the second amplifier stage 5.
  • a dry rectifier H for instance a copper oxide rectifier, a condenser I8 and resistances I9 and 20 are inserted in the plate circuit it of the other diode which is normally used (see Fig. 2).
  • the negative tension obtained serves for the control of the output tube 6 which acts as direct current amplifier.
  • the direction of the rectifier connection i1 is arranged in the same manner as rectifier I l, except that this circuit is so adjusted as to have a time constant which is larger than that of the circuit of the first tube. This arrangement eliminates blocking of the second stage before the increase of the first stage 4 has been reduced by the adjustment.
  • Condenser I8 is connected to grid 8 of tube 5 across resistance 23. (In Fig. 2 this connection is to the ground.)
  • the two first tubes are polarized only by the voltage drops produced by the plate currents traversing resistances 2
  • Fig, 6 illustrates various shapes of signals received by an apparatus including an automatic adjusting device such as described in connection with Fig. 5, these signals being transmitted under the same conditions as those whose shapes, at the receiving station, are shown in Fig. 4. It may be noted that for attenuations from 0 to 30 db., the distortion of the length of the signal amounts to approximately 10%. In other words, it is possible to obtain accurate operation of the teleprinter system from 0 to 30 db.
  • Method of simultaneous telegraph and telephone transmission over a single channel which includes transmitting telephone signals at frequencies extending from the possible minimum to over 1200 cycles, and also at frequencies extending from over 1700 cycles to the possible maximum, transmitting telegraph signals over a frequency band lying between 1200 and 1700 cycles, amplifying received signals and suppressing the effect of signal drag by temporarily reducing the amplification during the length of the signal proper and during the passage of the signal drag.
  • the method of transmitting telegraph signals over a telephone transmission channel which includes setting aside from the telephonic frequency range a predetermined frequency band in the region near the mean value of the telephonic frequency range, transmitting telegraph signals over said set-aside frequency band, amplifying received telegraph signals and suppressing the effect of signal drag by temporarily reducing the amplification during the signal proper and during the passage of the signal drag.
  • the method of simultaneous telegraph and telephone transmission over a single transmission channel which includes setting aside a predetermined frequency band in the region near the mean value of the telephonic frequency range, and of relatively narrow range as contrasted with the frequency range of the telephone signals transmitted, transmitting telegraph signals over said set-aside frequency band, and transmitting telephone signals of frequencies both above and below said set-aside band.
  • the method of simultaneous telegraph and telephone transmission over a single transmission channel which includes transmitting tele- 7 graph signals in a frequency band within the limits of the telephone frequency band and spaced from the edges thereof and simultaneously transmitting telephone signals in the portions of the telephone frequency band above and below said telegraph signal band.
  • a system for simultaneous transmission of telegraph and telephone signals over a single transmission system comprising means for transmitting telegraph signals in a predetermined frequency band and means for simultaneously transmitting telephone signals at frequencies above and below said band.
  • a system for simultaneous transmission and reception of telegraph and telephone signals over a single transmission system comprising means for transmitting telegraph signals in a predetermined frequency band over said system and means for simultaneously transmitting telephone signals at frequencie above and below said band over said system, means for receiving said telegraph signals comprising means for eliminating signals outside of said band and means for receiving said telephone signals comprising means for eliminating signal within said band.
  • said frequency band is no greater than 300 cycles per second in width and is centered substantially at 1500 cycles per second.
  • the method of transmitting telegraph signals over a telephone transmission channel which includes transmitting telegraph signals in a frequency band within the limits of the telephone frequency band and spaced from the edges thereof, receiving and amplifying said signals and suppressing the effect of signal drag by temporarily reducing the amplification during the signal proper and during the passage of the signal drag,
  • a system for transmission of telegraph signals over a telephone transmission channel com prising means for transmitting telegraph signals in a frequency band within the limits of the telephone frequency band and spaced from the edges thereof, means for receiving and amplifying said signals and mean for suppressing the effect of signal drag comprising means for temporarily reducing the amplification of said amplifying means during the signal proper and during the passage of the signal drag.
  • a system for transmission and reception of telegraph signals over a telephone transmission channel comprising means for transmitting telegraph signals in a frequency band Within the limits of the telephone frequencies and spaced from the edges thereof, means for receiving and amplifying said signals, automatic volume control means to bring said telegraph signals to an appropriate level, said automatic volume control means being prolonged in action whereby they act on the telegraph signal drag as Well as on the signal proper and the amplitude of said drag is always kept at a relatively low level with regard to the telegraph signal proper.

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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)
US475687A 1941-10-27 1943-02-12 Electrical communication system Expired - Lifetime US2426222A (en)

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Application Number Priority Date Filing Date Title
FR2426222X 1941-10-27

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US2426222A true US2426222A (en) 1947-08-26

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US (1) US2426222A (enrdf_load_stackoverflow)
FR (1) FR959719A (enrdf_load_stackoverflow)

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3875339A (en) * 1972-09-05 1975-04-01 I I Communications Inc Variable bandwidth voice and data telephone communication system
EP0312693A3 (en) * 1987-10-22 1990-08-16 Grundig E.M.V. Elektro-Mechanische Versuchsanstalt Max Grundig Holland. Stiftung & Co. Kg. Method for speech encryption with simultaneous data transmission in narrow band transmission system
BE1004961A4 (fr) * 1989-08-16 1993-03-09 Akkumulator Es Szarazelemgyar Procede pour la preparation d'une masse active de meilleure qualite a partir de dechets de masse active formes pendant la fabrication d'accumulateurs au plomb.

Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1998824A (en) * 1932-06-10 1935-04-23 Bell Telephone Labor Inc Method and system of speech transmission
US2106352A (en) * 1935-03-15 1938-01-25 Bell Telephone Labor Inc Teletypewriter station
US2121287A (en) * 1937-03-03 1938-06-21 American Telephone & Telegraph Composite set
US2150241A (en) * 1935-02-23 1939-03-14 Ibm Communication system
US2300775A (en) * 1940-08-31 1942-11-03 Bell Telephone Labor Inc Communication system
US2323880A (en) * 1940-12-26 1943-07-06 Zenith Radio Corp Wave amplitude limiting device
US2332494A (en) * 1942-04-23 1943-10-26 Bell Telephone Labor Inc Signaling system

Patent Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1998824A (en) * 1932-06-10 1935-04-23 Bell Telephone Labor Inc Method and system of speech transmission
US2150241A (en) * 1935-02-23 1939-03-14 Ibm Communication system
US2106352A (en) * 1935-03-15 1938-01-25 Bell Telephone Labor Inc Teletypewriter station
US2121287A (en) * 1937-03-03 1938-06-21 American Telephone & Telegraph Composite set
US2300775A (en) * 1940-08-31 1942-11-03 Bell Telephone Labor Inc Communication system
US2323880A (en) * 1940-12-26 1943-07-06 Zenith Radio Corp Wave amplitude limiting device
US2332494A (en) * 1942-04-23 1943-10-26 Bell Telephone Labor Inc Signaling system

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3875339A (en) * 1972-09-05 1975-04-01 I I Communications Inc Variable bandwidth voice and data telephone communication system
EP0312693A3 (en) * 1987-10-22 1990-08-16 Grundig E.M.V. Elektro-Mechanische Versuchsanstalt Max Grundig Holland. Stiftung & Co. Kg. Method for speech encryption with simultaneous data transmission in narrow band transmission system
BE1004961A4 (fr) * 1989-08-16 1993-03-09 Akkumulator Es Szarazelemgyar Procede pour la preparation d'une masse active de meilleure qualite a partir de dechets de masse active formes pendant la fabrication d'accumulateurs au plomb.

Also Published As

Publication number Publication date
FR959719A (enrdf_load_stackoverflow) 1950-04-04

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