US1788508A - Submarine-signaling system - Google Patents

Description

SUBMARINE SIGNALING SYSTEM Filed 'July 14. 1927 r be A05 mv M. Gum/.5

denser as viewed from the cable.

Patented Jan. 13, 1931 om n A r-s8 Ti rrie' AUSTEN M. CURTIS, or EAST ORANGE, NEW JERSEY, Ass ornon 'ro wusrnnn nLEoTn-ro COMPANY, rnconronarnn, or NEW. Yon ,.1\T-;; Y A COREORAT-ION. or-nnw YORK SUBMARINE-SIGNALING sir STEM Application med July 14,

This invention relates to submarine signaling systems and more particularly to, those systems in wh ch termmal equipment is designed to operate to permit the trans-f missien of signals over a submarine'cable at high speeds. 4 I

An obJect of the lnvention is to facllitate the adjustment of the verylow frequency "these wave forms as toincrease the legibility of the signals recorded at the terminal. This. apparatus which is, generally referred to as a shaping or distortion-correcting network, may be used in combination with both the sending and the receiving equipments, and

such combinations used in connection with high speed-signaling aredisclosed in Patent 7 granted to A. M; Curtis on April 12, 1927. j

The circuits used at the sending terminal, and with which the present invention is particularly concerned, take the form of an impedance element which'has a low value as compared withthe characteristic impedance of the cable andwhich is, in effect, a shunt path to earth on both the cable as viewed from the transmitter and on its associated transmitter and shunted sending con- At first a low resistance was employed alone in the shunt path'to earth but it was found tohave the disadvantageof shunting to earth the larger part of the extremely low frequency components of the transmitted signals, thereby requiring that the receiving. apparatus be adjusted to be rather. sensistive to these very low frequency signal components. This, inisome cases, may cause an objectionable amount of earth current to flow thru the receiving networks. In a simplex oper-' ated submarine telegraph system the establishment of this earth current during the operation of switching from sending. to receiving produces a heavy surge thru the ampli- 1927. Serial 1101205561.

fier and this surge tends tomomentarily dise place the zero of the signal Therefore, in "order to reduce the strength ofearth current and switching surges and toallow the use of a receiving shaping network which wasrelatively insensitive to currents offrequencies .approac'hing direct current; a condenser of large capacity, that is, one of the order of several hundred ,microfarads, was inserted in series withthe low resistance elementin the shunt "path to earth." This condenser is ofsuch capacity that ityhas little influence on the act-ion of the earth pathshunt resist anceat any but the'extremely lowfrequency components of the signal. v

According to the present. invention a partialcorrection, orshaping, of the extremely low frequency con iponentsof the signal wave 'form is effected at the transmittingterminal, thereby reducing to a considerable degree the amount of correction which would otherwise be necessary at thereceiving terminal. This partialcorrectioii is made by connecting in shunt to the large'capacity condenser a vari;

by reference to the following detailed descriptiontaken in connection with the single figurefof the accompanying drawing. In the drawing it will benoted that the equipment, shown in detailgisthat required for transmitting signals from one. end of a cable of a submarine telegraph system arranged for simplex operation This equipment is some whatsimilarto that sho'wnin Fig-11 of the CurtisPatent No. .,1,624,396 to which reference has previously been made.

Referring to the drawing, a single core submarine cable 1 is terminated in a twin core section of submarine. cable 2. .One core 3 of the twin-core section is spliced atone Y can be connected in its upper position to the I end to the single core cable 1 and atthe other end is connected to a switch 4. Theswitch signal receiving apparatus R and inits lowerposition to the transmitting equipment T,

the individual elements of which will be hereinaiter designated. The other core 5 of the twin-core section is connected at the sea end thrua resistance G'to a conductor in Contact with the seafi'va'ter. In the particular arirangement shown the resistance is connected to the cable armor WlIES at'poln-tzl' and a con ventional ground connection, shown by dot ted lines, is used to indicate that the armor Wires are grounded. The core 5, together '-\Vltl1 the network 6 grounded at the point/7,

constitutes a cable-balancing Ireturn circuit. Thesliore endof core 5 is connected to the receiving apparatus R. A type of core suit able for both the single core cable 1 and twin core section 2 comprises a copper conductor provided with a Wrapping of a mag? V netic material, such as the nickelronalloyy generally known 1n the art as permal-loy to niicrofarads, with shunting resistance 11 of 5,000 to 100,000 .ohms. As hereinbcfore explained the transmitting equipmentT til may be connected to the core of the tWincore se'ct1on2 by meansot sw1tch4 in ts lO'WQIQPOSltIOIL. On'e termunalott the transmitter equipment is then connected to the core 3, While the other terminal is grounded at an extra earth 12 at sea. Connectedracross the cable terminals is a low resistance shunt path comprising resistance-13 of 50 to 200 ohms and condenser 14 of several hundred microfarads in series, with a relatively high resistance 15 shunted acrossthe condenser. Resistance 15 may range in magnitude from about one hundred ohms to many thousand ohms. v a I The characteristic impedance of cable 1,is approximately 400 ohms for voltages of the higherfrequencies involved in signaling, but it is evident that for theivolt ages, of very 10W frequencies this can not be the case, For

example, at zero fifequency,-'the character-is.

tic impedance of the cable is its direct current resistance; and in "the case "of an actual cable betiveenNevv Yorka rd resistance is about 4,600 ohms. At first, the principal difficulty in correcting the jdis'ton 30 cycles a second lay in reducing sn'fiiciently the relatively enormous amount of signalthe Azores, this ing components ofthe lower frequencies of shaping at both the transmitting and receiving terminalsot the cable. The shunt resistance 13 added materially in'acc'omplishing this result, but, as stated above, too great a parrot the low frequency components of "then-ansmi'tted signal; was shunted tonal-tn.

In 'ordcrito reduce the amount'of low -frequency Components flowing to earth'thru rcsistance l feetidensm 14 was inserted in series vith the shunt resistance 13, this con denser beings) large that it has little influ ence onthe action of the shuntresistance,13 at any but, the eiitremelyfloivfrequency components of the signal; Thedistortion ot' the signal wave for-in produced by these extreme- '.1 low frequency components had to becojrrected by the shaping network at the rc'ceiving station. The addition of variable resistance;l5 in shunt to condenser 14 permits the amplitude of the signal components of low frequencies transmitt'e'dto the cable to be conm-ollediat the sending station, there by facilitatingmarkedly the adjustment of the correcting networks at the receiving station. V

What s claimed is:

" "1. A cablesignaling system comprising a cablet nieans for impressing si naling .cur-

' rent on said cable, apath connected in parallel With'said cable as viewed from said means and having an im'pdance'loiv'in compariso'n ivith the 'chai'actericti'c impedance of. the cable, said path, beingj conductive to direct current but including a high resistance and a high capacity condenser forregulating componentsshunted to eartln iyhereby surges on the cable due to excessive 10w fret'p 'ency ion the amount of the extremely low frequency 2. A cable signalingsystein comprising a.

cable, means for impressing a signaling current on said cable, a path connected in 'p'arallel ivit h said cable, as viewed from'said means and having'a low impedance for high frequencies in comparison to the characteristic impedance of the cable and a high resistance forfthe very low'frcquencies, said path comprising a low resistance element anda large condenser in series therewith, and arelatively high resistance in shunt to said condenser.

3. A cable signaling system" con'iprising a cable, an impulse m-ansmitttma sending condenser v connected between said trans- "mitter and said cable. and a path to earth having an impedance low in comparison tvith the characteristic impedance of the cable, tion of this cable for signaling speeds above connected at a point between said cable andfsaid condenser, sa1d path comprising a low resistance and a large condenser in series therewith, and a relatively high recuit connected in shunt to said cable as viewed from said transmitting apparatus,

said circuit comprising a low resistance, a

condenser so large that its effect upon the impedance of said series circuit except at very low frequencies is negligible, and a comparatively high resistance in shunt to said large condenser for overcoming the effects of said large condenser at the very low fre-- quencies. I

5. In a submarine cable signaling system, a submarine cable, signaling apparatus associated therewith, the characteristics of said cable and said apparatus being such that certain frequency components of the signaling current are transmitted thereover with less attenuation than are other frequency components, and a path to earth connected at a point between said signaling apparatus and said cable, said path comprising a low re sistance and a large condenser, and an adj ustable relatively high resistance in shunt to said large condenser. r i

6. A submarine cable signaling system comprising a submarine cable loaded with an alloy comprising nickel and iron having high )ermeabilit at lowina 'netizin forces a sending condenser, an impulse transmitter connected to saidcable thru said sending condenser, and a resistance path to earth connected between said cable and said condenser being of low value compared with the characteristic impedance of the cable, said path comprising a low resistance and a condenser so large that its effects on the low resistance except at very low frequencies is negligible, and a comparatively high resistance in shunt to said large condenser for overcoming the effect of said large condenser at the very low frequencies.

7. A, cable signaling system comprising a cable, means for impressing signaling current on said cable, a path connected fixedly at a point between said means and said cable baring an impedancewhich is low in comparison with the characteristic impedance of the cable, said path being conductive to direct urrent and including an adjustable high resistance and a high capacity condenser.

8. A cable signaling system comprising a cable, an impulse transmitter, a sending condenser connected between said transmitter and said cable, and a path to earth having an impedance which isflow in comparison with the characteristic impedance of the cable and being fixedly connected at a point between said sending condenser and said cable, said path comprising a low resistance and a large condenser in series therewith and an adjustable relatively high resistanc in shunt with said large condenser.

In witness whereof, I hereunto subscribe my name this'12 day of July, A. D. 1927.

AUSTEN M. CURTIS.

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