US1815657A - Submarine cable system - Google Patents

Description

y 1931- R. E. A. PUTNAM 1,815,657

' suBuAnmE CABLE SYSTBII Filed March 6. 1930 2 Sheets-Sheet l SPEClAL SHORE END l I uong TERMINAL APPARATU$ F "'CABL secT|oN- P- SEA I I l 24 COMMON SEA JUNCTION POINT INVENTOR RALPH E.A. PUTNAM ATTORNEY July 21, 1931. R. A. PUTNAM 4 1,315,657

SUBMARINE CABLE SYSTEI Filed larch s. 1930 2 Sheets-Sheet 2 a H.P. FILTER H. P. FILTER SEA Juucnou POINT LB FILTER 4- DELAY 34 NETWORK J TELEPFDM 8 TELEGRAPH LE FILTER I Q I l PSI-DE TERMIML APPARATUS-*DK-SPECIAL SHORE END CABLE SECTIONr-DEEP SEA CABLE-i l I TELEPHONE E? nmuzrzn TELEGRIPI' l t LP. FILTER FLRFILTER COMMON DELAY NETWORK HR FILTER s4 LRFILTER HR FILTER 4 INVENTOR RALPH aA. PUTNAM Patented July 21, 1931 meri -an ,srn'res Parana re 4R'ALIP'H E. A. 'IPIITN'AM, OF 'MGUNKAIN LAKES, NEX JiElSZGEOR TO INTER- NATIONAL *COMll'LU'NICATIOHS LABORATOREES 'i Ll'UORE- GBATE S'UIBMARINE CABLE SYSTEM Application filedMareh c,

This invention relates to an improvement in submarine cahle telephony and telegraphy and has particular reference to the systems whereby telephone and telegraph messages aretransmitted over the same cable simultaneously in both directions.

' lhe object of this invention is the produc- 'tion eta submarine cable for the simultaneous transmission oftelephone and telegraph signals' which Wil substantially reduce the amountot interference to the telephone signals caused by the large 11C. telegraph currents impressed on the'cable at the sending end.

Another object of this invention is the production or a cable system for the simultaneous n'ansmission of telephone-and telegraph signals which Will eliminate interference caused by transmitted telephone and telegraph currents passing into their respective local receiving circuits,

Another object of thisinventionis the sim 'plification of the liltercquipment normally required in the usual form of cable circuit, and the consequent reduction in the amount oi -filter equipment necessary and'in the cost of this equipment.

In accordance with the objectso'f'the invention, special shore end sections of the cable are provided, each containing two or more special conductors Which merge With the main deep sea cable at junction points remote from shore, and whose shore ends are respectively joined tothe local telephone and telegraph transmitting circuits andtothelocal telephone and telegraph receiving circuits, and intermediate the local transmitting and receiving circuits is interposed a-delay network circuit.

In the drawings, Fig. 1 represents one end of the cable and a portion or" the local telephone and telegraph transmitting and receivi circuits, and a delay network circuit interposed between the local transmitting and receiving circuits.

Fig. 2 is similar to Fig. l-but shows inductive coupling of the local transmitting and receiving circuits and their respective branches of the shore end cable section in place of theconcluctive couplingfloif Fig. 1.

the loadin material.

1930. Serial No.433fi8.

3 is sim lar to Fig. l, Withthe exception that the ay netwerl: connections are differently arranged undone-Way devices are shown in tl elocal transmitting and delay network ci rcuits.

Fig. 4 is similar to Fig. 3 but .illustrates'a modification oi": the connectionsbetween the delay network circuit a d the local receiving circuits SlIOJVIl in Fig. 3.

in order to operate loaded submarine cabledesigned to carry telephone frequencies economically it is necessary advantage betalzen of the ability of the individual conductors not only to operate in dupleir but to transmit several telegraph channels simul- 'taneously Withthe telephone channels.

One of the major difficulties usually encountered in composite operation of the ordinary duplex submarine cable is 'the'problem of maintaining a substantially perfect 'arti iicial line balance so to prevent locally transmitted s gnals of either telephone or telegraph frequencies from reachi their respective associated local receiving circuits.

A second difficulty results fromthe tendency or the large DJC. telegraph currents at the sendingend of the cable to cause partial saturation otthe cable loading material and thereby introduce harmonics of the-telegraph signals intothe cable circuitby reason of the non-linear magnetization characteristic o f The portions of these spurious frequencies so introduced which fall within the voice frequency range are able to pass bacs into the local telephone channel, anc may'thus decrease seriously the intelligibility 01 any speech currents that maybe received simultaneously.

a To eliminate the above difficulties it is proposed to use a cable with split shore end sections merging with the main cable at a point remote'from shore, one branch of each shore end section to be used a common transmitting branch and the other as a com-- men receiving branch, these branches to "be conneeled with thelocal-transmitting and receiving circuits respectively, and the local transmitting and receiving circuitsto be con nected by a circuit containing a delay=net- Work.

While this torin or" cable construction has one tradurutage 111 that an impedance 1r- 1 .1. 7 l'ejl'llllllltj .lsillltl lll lllt Sill jllllCllOil pOllllS where the shore e1ulsect1onsiuerge with the main cable, such as to cause an appreciable transmission loss, it is believed that this factor is of small importance in comparison with the advantages to be gained by the use of this type of cable.

In Fig". 1 the invention is shown as applied to a twoway simultaneous telephone and telegraph cable system, one end or th main cable and the corresponding special shore end cable section and local circuits only, being shown, as the construction at the two ends of the cable is identical. The telephone signal current passed. from the telephone transmitting, station 1 to the local telephone transn'ii ing circuit where it is impressed on conducto 3 and passed through a high pass filter 8 to unction point at where the local telephone transmitt circuit merges 'ith the common transmitti c; branch of the special shore end section oi. the cable. The telegraph current is in: (l from the telegraoh station to the local telegraph transmitting circuit where it is impressed on conductors G and passed through a low pass filter 7 and junction point 8 to junction point 4 where the lo *al telegraph t 'ansmitting circuit merges with the common transmitting branch of the special shore end section of the cable. When the telephone signal currents reach junction point l and the telegraph signal currents reach junction point 8 eaca current is divided and approximately one-half of each current is impressed on the common transmitting branch of the shore end cable section 9 and pa .es to the sea junction point 10 where a portion of each signal current is passed to conductors 11 of the deep sea cable and thus the distant receiving terminals. By reason of the impedance irregularities presented by the sea junction point 10. a portion of each transmitted current is reflected back over common receiving branch conductors 12 to junction point where these conducto connect with the local telephone and telei ..ph receiving circuits. T he component part of each signal current passed into the common transmitting branch conductors 9 from junction points 1 or 8 is passed into a delay netv-iork 14, a do 3e well known in He art and which has a time constant and a1 enuatiou constant equal to that of the loop formed by the common transmit.- ting branch 01 the shore end cable section 9, sea junction point 10 and the common receirinn branch of the shore end cable section 12 so that the signal currents reaching junction point 15 a'l't leaving: the delay network 1&- are identical, with their component signal currents reflected back from the sea junction point 10. except that the signal currents passing through the delay network are reversed in polarity either in the delay network itseli or at some other point in the (lelay network circuit, with the result that the two components of each signal current cancel each other and the reflected currents are thereby eliminated before they pass filters 16 or 17 and so are prevented from reaching receiving station 18 or 19 over local receiving conductors 20 or 21 respectively.

Incoming signal currents of both telephone and telegraph frequencies, arriving over main cable conductors 11, will obviously divide on reaching sea junction point 10, approximately one-half of each signal current passing over conductors 12 to junction point 13 where the signal currents of the two frequencies will be separated by filters 16 and 1? and will be passed to their respective receiving stations 18 or 19 over conductors 20 or 21 respectively. The component part of the received signal currents will pass from sea junction point 10 over conductors 9 to junction point l where each signal current will again be split and a portion of the current will pass into the delay network 14 and consequently into the local receiving circuits at junction point 15. By reason of the fact that the portions of the signal currents flowing: through the delay network circuit will be attenuated and retarded in phase and will also be reversed in polarity, they may tend to interfere with the directly received signal components under certain conditions. If, however. the attenuation of the delay network is of the order of 20 decibels or higher. corresponding approximately to a special shore end cable section of at least 100 nautical miles in length, it is probable that any interference produced will not be objectionable. For this reason the special shore end cable section used in this system should be between 100 and 500 nautical miles in length, although under certain circumstances a shore end section of even nautical miles in length might be satisfactory. The exact determination of the length of this section is, however, not made a part of this invention.

The preceding discussions and figures relate to methods wherein the cables are conductively connected to the terminal. telephone and telegraph equipment. Under conditions where it is desired to protect the cable from dangerous potentials to which the terminal apparatus or associated land lines may be exposed, or alternatively to keep out of the terminal receiving apparatus certain types of interference currents which may be induced in the cable conductors. the conductive form of coupling may be replaced advantageously by inductive coupling utilizing transformers shown in 2. .Vhile the transtorn'iers shown in Fig. 2 apply to both the telephone and telegraph signal currents it will be obvious to those skilled in the art that alternative arrangements may be readily substituted whereintransformers are introduced .only in the telephone branches,:leavingcthe'itelegraph branches connected :metalli'cally where local conditions indicate that .lll'llS is the more advantageous method.

WViththe above exception the system shown .in Fig. 2 is identicalinconstructionnndoporation with thatsetiforthzin Figdcandtheretore only so muchofthe system as'has been "modified will be described. "Inthis system, instead or" connecting thedelay networkcircuit metallically with the local transmitting and local receiving circuits, the local tele phone and telegraph transmittingcircuits are extended from junction :poin t22to winding .23 of transformer 24, the alternate windings 25 and 26 of which are electrically balanced and are connected to the common transmitting .branch oi the special shore end cable section and to the input endofthe delaynetwork circuit respectively. 'iLikew-isethe local .telephone and telegraph receiving circuits are extended fromjunction point 27 to winding 28 or" a second-transformer 29, the-a lternate windings SO and 31 of whichare-electrically balanced and are-connected to the common receiving branch of the special shore end cable section and tothe output end of the delay network circuit respectively.

In Fig. 3 is shown a system-designed for use with special shore end cable sections of shorter l ngth than will operate advantageously with the systems previously illustrated. This system is identical in construction and operation withthat shown in Fig. l exccpt tha. certain one-Way devices have been added to the circuit and: the connections modified accordingly, and theretore :only so --much of the system as has been modified will be described.

In this figure the input side o t the-delay :network circuit, instead of being connected to the local telephoneand telegraph transmitting circuits at'j-unoti'on "points 4 and 8 respectively, as in Fig. 1, is=connected to said circuits at junction points 32and 33 respectively. In the circuit connecting the delay network 34 with unction point 32a one-way device 35, consistingof vacuum tu be amplifiers orrelays, and ahigh pass filter 36 have been inserted; similarly in -the circuit connecting the delay network 34 with juncion point one-way device- 37 anda low pass ltcr '38 have been inserted. Que-way devices of the tvpe just described have also been inserted' inthe local telephonean d telegraph transmitting ircuits, min. 39 and 40. These modifications :do not materially alter the operation of the system in regard to transmitted signalcurrents. e transmitted telephone signal currents impressetl on conductors 41 divide at 'jHRCtlOIIPOlHiL BQ, approximately one-half oi the current passing through one-way device39 andthrough high pass filter 42 to the common transmitztingibranch of :the specialishore .end cable section, 13116 remaining component f .each signal .currentrpassing -over conductors 43 :through .one-.way device and high ass 1filter'36t0 the delay network 34. The transmitted telegraph signal currents impressed .on conductors 44 divide at unction1point33, approximately onehalf of theisignal current passing through one-way device and low pass filter 45 to the common transmittingv ation of the system shown in *Fig. 3 is 111 31 :terially diiierent from that ofthe previously described systems in regard to the incoming signal currents. The incoming signal cur- Irents'are'divided at the sea junction point, approximately one-half'of each signal:current passing directly over thecommon receiving branch ofthe special shore end cable section to one ofthe receiving stations. The remaining component of the signal current passes over the common transmitting branch .ofthespecial shore end cable section to j uncllI-lOIl "point .47, and through-either filter '42 -G1"i4:'5t0 one-way device 39 or '40, where the currents will be stopped and thus prevented fronrpassingthrough the delay network 34 zinto the localreceiving circuits and so interd'ering'with the received signals. By reason .of the iactthat .thecomponent partsot the signal currents are so stopped before reach- :ingithe delay network there is no need for a special shoreendcable section of such. length that it will attenuate and delay the signals passingithrough the delay network to a point 'where there can'be no interference lit-l'lvth directly received signals, and the special shore .end .cable'section may, in-this case, be less-than nautical miles in length, although the exact determination ofthe length ofthis'section is not made part of this invention. v

The system shown in Fig. 4 is identical in construction and operation with that illus vtrated in Fig. 3 except that it shows an alternative method of connecting the delay network circuit with the local telephone and telegraphreceiving circuits. Only so much of the system as has been modified will be described. 'Under this modification the delay network circuit is not connected directly to the local telephone and telegraph receiving circuits as at point 48 of Fig. 3, but the telephonefsignal currents passing through the delay network circuit are'passed through junction point 49 to high pass filter 50 and from there to junction point 51 where said currents meet and cancel the locally transmitted telephone currents reflected back from the sea junction point and thus prevent such currents from reaching telephone receiving station 52. Likewise the telegraph signal currents passing through the delay network circuit are passed through conductors 53 to low )KISS filter 54 and from there to junction point 55 where said currents meet and cancel the locally transmitted telegraph currents reflected back from the sea junction point and thus prevent such currents from reaching telegraph receiving station 56.

What is claimed is:

1. The method of transmitting telephone and telegraph currents simultaneously in both directions over a submarine cable having special shore end sections merging with the main cable at points remote from shore and containing transmitting and receiving conductors, comprising impressing a portion of each current on the transmitting conductors and passing the component part of the current through a delay network circuit which so ati'ects the current that on passing into the local receiving circuit it cancels the current from the local transmitter which returns by way of the sea junction point and local receiving conductors to the local receiving circuit.

2. The method of receiving telephone and telegraph currents simultaneously over a submarine cable having special shore end sections joined to the main cable at points remote from shore and containing transmitting and receiving conductors, whereby the signal currents on reaching the sea junction point at the receiving end of the cable divide, a part of each current passing over the common receiving conductors to the terminal receiving apparatus, the component part of the current passing over the common transmitting conductors from which a portion of it passes through the delay network where it is so attenuated and delayed that it offers negligible interference to the directly received signals, when it enters the local receiving circuit from the delay network circuit.

3. The method of transmitting telephone and telegraph currents simultaneously over a submarine cable having special shore end sections containing transmitting and receiving conductors merging with the main cable conductors at junction points remote from shore, comprising impressing a portion of each signal current on the transmitting conductors and passing the remaining component of each current through a delay network circuit which so controls its magnitude, phase and polarity that on passing into the local receiving circuit it cancels the current from the local transmitter which returns by way of the sea junction point and the local receiving conductors to the local receiving circuit and comprises dividing the signal currents at the sea junction point at the receiving end of the cable, one part of each current passing over the common receiving conductors to the terminal receiving apparatus, the component part of each current passing over the com mon transmitting conductors from which a portion of it passes through the delay network which so attenuates and delays the current that on entering the local receiving circuit it offers negligible interference to the directly received signal current.

4. The method of transmitting telephone and telegraph currents simultaneously over a single submarine cable which comprises impressing a part of each signal current at the transmitting station upon common transmitting conductors extending from said station and merging with the main cable conductors at a junction point remote from shore, and passing the component part of each signal current through a delay network circuit interposed between the local transmitting and receiving circuits, which so affects the magnitude, phase and polarity of each current that on its passage into the local receiving circuit it cancels the component current from the local transmitter which is reflected from the sea junction point to the local receiving circuit over the common receiving conductors, and comprises dividing the signal currents at the sea junction point at the receiving end of the cable, one part of each current passing directly over the common receiving conductors to the terminal receiving apparatus, the component part 01' each current passing over the common transmitting conductors from which a portion of it passes through the delay network which so attenuates and delays the current that on entering the receiving circuit it offers negligible interference to the directly received signal currents.

5. The method of transmitting telephone and telegraph currents simultaneously over a single submarine cable which comprises passing the transmitted currents into a transformer where a part of each signal current is impressed upon common transmitting con ductors extending from said station and merging with main cable conductors at a junction point remote from shore, and pass ing the component part of each signal cur rent through a delay network circuit connected to the local transmitting circuits through said transformer, and connected with the local receiving circuits through a second transformer similarly placed, said dclay network circuit so affecting the magnitude, phase and polarity of each current that on its passage into the local receiving circuit it cancels the current from the local trans mitter which returns by way of the sea junction point, local receiving conductors and sec ondtransformer to thelocal receivin'g'circuit. i

'6. The method of transmitting telephone and telegraph currents simultaneously lover a single submarine cable which comprises passing apart of the telephone signal current through a one-way device and a high pass filter and passinga part of the telegraph signal current througha one-way; de-

vice and a low pass filter and thereafter impressing said portions of both currents upon common transmitting conductors extending from the transmitting station and merging with the main cable conductors at a junction point rem'ote'ifrom shore, and passing the "component part of the telephone current throu haseparateone way device and high pass iilter and passing the component part of thetele'graph "current through a separate one-Way device and low pass filter and thereafter passing said parts of :both currents through a delay network circuit interposed between the local transmitting and receiving circuits which so afiects the magnitude, phase and polarity of each current that on its passage into the local receiving circuit it cancelsthe component current from the local transmitter which is reflected from the sea juncrtionpoint to the local receiving circuit over the "common receiving conductors, and comprises dividing the signal: currents at the sea junction point at the receiving end of the cable, one part of each current passing directly over the common receivingconductors to theterminalreceiving apparatus, the component part of each current passing overthe common transmitting conductors to the transmitting circuit whereit is stopped by said one-Waiy devices inserted in the local transmitting circuit before it passes into the delay network circuit. 4 i 1 A=submarinecable-system comprising in combinatioma local telephone transmitting circuit, a local telegraph transmitting circuit,

loaded transmitting conductors, loaded re ce-iving conductors, said transmitting and receiving conductors merging with loaded deep sea cable conductorsat "a vsea junction point remote from shore, and a delay network circuit joining said local transmitting and rea remote from (shore, and a delay network circuit joining the said local transmitting and receiving circuits, and'having a time constant and attenuation constant equal to that of the loop formed by the transmitting and'receiving conductors and the sea junction point;

. 9. A submarine cable system comprising in combination, a local telephone transmitting circuit, alocal telegraph transmitting circuit, a local telephone receivingcircuit, a local telegraph receiving circuit, taper loaded transmitting c nductors, taper loaded receiving conductors, said transmitting and receiving conductors merging with taper loaded deep sea cableconductorsat asea'junction point remote from shore, and a delay network circuit joiningsaid local transmitting and receiving circuits and having a time constant and attenuation constant equal to that of the loop formed by the transmitting and receiving conductors and the sea junction point. V

10. A submarine cable system comprising in combination, a local telephone transmitting circuit, a local telegraph transmitting circuit, loaded transmitting conductors, said local transmitting circuits being connected to said conductors through a transformer, a local telephone'receiving circuit, a local tele graph receiving circuit, loaded receiving conductors, said local receiving circuits being connected to said conductors through'a transformer, both of said conductor groups being merged with loaded deep sea cable con ductors at a sea junction point remote from shore, a delay network circuit joining said local transmitting andfreceiving circuits through said transformers and having a time constant and attenuation constant equal to that of the loop formed by the transmittin and rec'eivinc conductors and the sea junction point.

'11. A submarine cable system comprising in combination, a local telephone transmit ting circuit, a high pass filter in said circuit, a local telegraph transmitting circuit, a low pass filter in said circuit, a local telephone receiving circuit, a high pass filteriin said circuit, a local telegraph receiving circuit, a low pass filter in said circuit,'loaded transmitting conductors, loaded receiving cons ductors, said transmitting and receiving conductors merging with loaded deep sea cable conductors at a sea junction point remote from shore, and a delay-network circuit joining said local transmitting and receiving circuits and having a time constant and attenuation constant equal to that of the loop formed by the transmitting and receiving cables and the sea unction point;

in V

phone receiving circuit, a high pass filterin said circuit, a local telegraph receiving circuit, a low pass filter in said circuit, loaded transmitting conductors, loaded receiving conductors, said transmitting and receiving conductors merging with loaded deep sea cable conductors at a sea junction point remote from shore, a dclaynetwork circuit having a time constant and attenuation constant equal to that of the loop formed by the transmitting and receiving conductors and the sea junction point, and connected with the local telephone transmitting circuit by a circuit containing a one-way device and a high pass filter, and connected with the local telegraph transmitting circuit by a circuit containing a one-way de vice and a low pass iilter, and connected with the local telephone and telegraph receiving circuits.-

13. A submarine cable system comprising in combination, a local telephone transmitting circuit, a one-way device and a high pass filter in said circuit, a local telegraph transmitting circuit, a one-way device and a low pass filter in said circuit, a local telephone receiving circuit, a high pass filter in said circuit, a local telegraph receiving cireuit, a low pass filter in said circuit, loaded transmitting conductors, loaded receiving conductors, said transmitting and receiving conductors merging with loaded deep sea cable conductors at a sea junction point remote from shore, a delay network circuit having a time constant and attenuation constant equal to that of the loop formed by the transmitting and receiving conductors and the sea junction point, and connected with the local telephone transmitting circuit by a circuit containing a one-way device and high pass filter, and connected with the local telegraph transmitting circuit by a circuit containing a one-way device'and a low pass filter, and connected with the local telephone receiving circuit by a circuit containing a high pass filter, and connected with the local telegraph receiving circuit by a circuit containing a low pass filter.

l l. A submarine cable system for simultaneous two-way communication comprising in combination a cable, telephone and telegraph circuits connected to said cable, means for impressing signals upon said circuits, means for separating the components of the impressed signals, and means for returning and cancelling a portion of one component of the current so divided.

15. A submarine cable system for simultaneous two-way communication comprising in combination a cable, telephone and telegraph transmitting and receiving circuits connected to each end of said cable, means for impressing signals on said transmitting circuits, means for dividing each impressed signal into several component parts, and

raises"? means whereby a portion of one of the unused signal components can be returned to the local receiving circuit and cancelled.

16. A submarine cable system for simultaneous two-way communication comprising in combination a cable, telephone and telegraph transmitting and receiving circuits connected to said cable, means for impressing sigpals upon said transmitting circuits, means I01 separating the several components of the signals so impressed, means for reflecting a portion of one of said signal components back to the local receiving circuit, and means for cancelling the signal component so reflected.

17. A submarine cable system for simultaneous two-way communication comprising in combination a cable, telephone and telegraph transmitting and receiving circuits connected to said cable, means for impressing signals upon said transmitting circuits, means for separating the components of the signals so impressed, means for delaying one of said signal components.

18. A. submarine cable system for simultaneous two-way communication comprising in combination a cable, telephone and telegraph transmitting and receiving circuits connected to said cable, means for impressing signals upon said transmitting circuits, means for separating the components ofthe signals so impressed, and means for delaying and reversing the polarity of one of said signal components.

19. A submarine cable system for simultaneous two-way communication comprising in combination a cable, telephone and telegraph transmitting and receiving circuits connected to said cable, means for impressing signals upon said transmitting circuits, means for separating the components of the signals so impressed, means for delaying and reversing the polarity of one of said signal components, means for reflecting a portion otthe remaining signal component back to the local receiving circuit and there cancelling it by means of the delayed signal component.

20. In a simultaneous two-way submarine signalling system wherein each end of the cable is divided into two branches, one for transmitting and the other for receiving, the method of preventing the signals transmitted at one end from interfering with the receiver thereat, which comprises impressing a portion of each transmitted signal directly upon the receiving branch in such magnitude, phase and polarity as to balance the signal component impressed on the receiving branch at the cable junction.

21. In a submarine cable system for simultaneous twosway telephone and telegraph communication wherein each end of the cable is divided at a point remote from shore into two branches, one for transmitting and the other for receiving, the method of preventing the signals transmitted at one end from interfering With'the receiver thereat, which comprises impressing a portion of each transmitted signal directly upon the receiving branch in such magnitude, phase and polarity as tov balance the signal component impressed on the receiving branch at the sea junction point. i

In Witness whereof, I hereunto subscribe my name this 5th day of March, 1930.

RALPH E. A. PUTNAM.

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