US2101699A - Alternating current signaling system - Google Patents

Description

e '1, 1937. M; BAESECKE ET M. 2,101,699

ALTERNATING CURRENTSIGNALING SYSTEM Fil ed May' 26, 1954 i was 1:34

37 41 J a i, 45 a 42 #6 8 i as I fl rl'i n fies ecke incl 1951125 Way ei- 5 L%% 8 WM 1ft torneys Patented Dec; 7, a 1937 -"anrsnnsma schatt, Siemensstadt,

Application wcorporationofqermany; I VI I my 26, 1934, semi No. 127,606

i I a v 12,101,099 I J I I CURRENT; SIGNALING G r n Aktiengesellnear Germany; u I

11 6mm" ar-302 I v r 1 4 Claims, I This invention relates to sig naling which negative resistancesare employed duce the energy lossesoi' signalfcurrents. More fcontrol impulses overlong distances to theseveral particularly this invention relates to alternating 5 current signaling systems such as telephone or telegraph circuits, especially when the signalcurrents are transmitted over long distancesplor inh stance .over underground or. submarine cables. 3

Inparticular, thisinvention airords advantages 3 when crystals, powder resistances, suitable metal I alloys and soon are used as negative resistances. oneQdifilculty which mustbe overcome in signaling' systems with negative resistances is the supply and control of the current biasing the f hegative resistances to a suitable pointot their II characteristic. Q'Ifhiscurrentis be transmitted over the Twholelsignal system whichcontains I widely 'difierentj, resistances, andjmustihave a relatively high input voltage; t According to the presentinvention special clrf cults are provided to I supply? thebiasing acin'rent to the several negativeresistances alonglthe lines. This supply circuit is soIdimensioned that a very goodinsulation exists between theindividual supply conductorswith respect to the relatively high voltage at the endsof the supply circuit. t I [A generic feature of the several specific embodirnents whichwe have disclosed in this application, is found in the fact that the voltage re telephone circuit. v I

" According to a further feature of our invention a separate line is provided to supply the biasing for cable purposes." I

Another. feature or the ifnve onsists in rnployingparts of the signaflinesor pecial cir cuits cooperating with se igqa 1mes,,for supplying bias currenttto"the' negative resistances. Another feature of this inventonconsists in superposing "alternating current channels in the signal current circuits to conduct the alternating currentto the pointsnat which negative resistances are located" and in rectifying this current to obtain a direct current for biasing purposes; This method afl'ordsthe advantage that the biasquired for the production of the biasing current is not applied between the two conductors oL aj current to a pluralityof signalggimes especially ing current can be conducted over direct current a blocking devices, such asforinstance transtormfrom the ends or section points oithe lines. I In .(9131'8945) I I I I I articular, according to our-inventionthe biasing urrent-xitseli'u-may be employed for transmitting,

negative resistances or to their control devices.

Further particularities otzthednvention will be i described 1 hereinafterv with. reference .to the ;examples shown instnqiaccampanymg drawing. 1 It i is to be understood that i the invention is not limited 7 to the precise I conditions or proportions herein set forth; as they may t bekreadily varied by thos'eskllled in the are I ,i Y ,i u 5 Fig. 1 illustrates diagrammatically a system for supplying biasing currentto atpluralityyof signal lines-by asingle separate line. I I I Fig. 2 representsa system for supplyinga biasling current only y signal lines without disturbingthewsignal transmission; l t

1 P 8;- 3 shows the'supplyot biasing current from a separate line to a two-wire circuit with parallel negative resistances, r it i Fig. 4 shows the superposition of an alternating current for biasing purposes in a signal line. In Fig. 1 .we have illustrated a section of a plurality oislines parallel to each other which are pr0vided f or. signal purpo e for instance this figure may represent a portion of a I telephone cable; For the sake-of simplieily'we hn've'shcw only two doublewire circuits fl 2 and 3, 4 respec may. I 'rne portio suus f atea is subdivided, ag

indicatedby the v tical dash-dottedlines. into I three subsectiohsinripihitzh negative resistances or well-known character, and, particularly, bodies of suitablesubstancesx'arearrangedin the con l by a capacity, indicated at, l6.

'I'heilatter as well astheIchokesare i to block the supply conductor 5 and'the circuits,

withres pectto one anotheragainstvoice currents flowing through a negative resistance,

Energy losses and crosstalk aretthuslprevented Instead of simple chokes, networksmay belprovided, preferably with a short circuiton the side middle (andfthefl 3. f i y I right portions ofFigglshowfthe sam a r ge; Q mht 1 ea h fj hasubsection a's-thenheiatthef of the I supply .conductor. The

extreme left. At the points l1, II we have indicated by the dotted lines that two further wire circuits may be connected to the supply conductor in the same number. For the return of the biasing direct current we may use a separate conductor or ground connections.

Particularly when using cables, the cable sheathing or the sea water may serve as the return conductor.

As shown in Fig. l, the negative resistances of one conductor are connected in series with respect to the biasing current, that is, the two ends of the negative resistances are connected to the same conductor of the supply circuit. According to our invention, it may be preferred in some cases to connect the negative resistances belonging to one circuit, alternately or in any other desired order to one or the other conductor of the supply circuit, in which case a separate conductor would be provided for each direction of the supplying current. The negative resistances may be also connected in parallel to thesupply conductor with respect to the same points of view as above described, to block the supply circuit against the signaling currents. The adjustment of the working points of the negative resistances may be effected by series or parallel connection of separate resistances or by suitable dimensioning of filters, or even when the same relations exist in all circuits, by connecting resistances in the supply circuit or by suitable dimensioning of the supply circuit. When using the invention for long distance lines, particularly in the case of parallel lines as in a cable, a preferable arrangement might be to provide several supply circuits or to arrange a main supply circuit and branch off at predetermined intervals, sub-supply circuits supplying biasing current to the corresponding sections. A supply circuit with a separate source may also be provided for several sections of a line or of a bunch of circuits.

To prevent a flow of the biasing current through the signal conductors from the two sides of the negative resistances, according to Fig. 1 the sections of these conductors between the negative resistances are blocked against the biasing current by capacities, such as indicated at l9, 2|) and 2|, 22 respectively, having only a low resistance to the passage of the signal currents. To enable a flow of direct current or of low frequency alternating currents for signal purposes through the conductors I and 4, suitable by-pass connections are provided. In Fig. 1 simple chokes 23, 24 are indicated for this purpose. These must be dimensioned to offer a high resistance to currents of higher frequencies such as, for instance, voice currents.

According to a further feature of our invention the two wires of a supply circuit are strung or arranged in such a manner that they will be separated from one another by insulation adequate with respect to the direct current voltage. Particularly in the case of cables, the two wires of the supply circuits are arranged in different parts of the cable, for instance in different wiregroups which are very well insulated from each other. I

In those cases where the mutual influence of the circuits traversed by the signal currents, for instance the cross talk in cables, is to be reduced to a minimum, asymmetrical distribution of the negative resistancesover the two conductors of a circuit is a preferable arrangement. It has been found that the mutual influence of the circuits can be diminished still more if the direction of the biasing current in the two conductors is chosen properly. According to our invention it is preferable to make the biasing current flow through the two conductors of a cable or open line circuits with negative resistances in the same direction in each of the conductors. This method aflords special advantages with lines having Pupin coils for damping attenuation, in addition to including negative resistances, because the Pupin coils are biased magnetically in case the biasing current flows through the two conductors in different directions, that is, with respect to the signal current. The biased Pupin coils would diminish. their attenuating effect and magnify the cross talk. Preferably, .the biasing current is supplied to the two-wire circuit at symmetrical points, for instance over the midpoint taps of transformers, chokes or other cross resistances, and is again taken off at such points.

Examples of such arrangements are illustrated by Figs. 2 and 3.

In Fig. 2 two double-wire circuits, for instance those of a telephone cable having conductors 25, 26 for transmission in one direction and conductors 21, 28 for transmission in the other direction, are shown as connected with the line terminals by transformers 29, 30 and 3|, 32 respectively. The midpoints of the transformer windings connected to the line are at the one end of the line connected to a battery 33, and at the other end of the 'line to a battery 34 supplying the biasing current to the negative resistances 35 46 connected in the line. The conductors 25, 26 and 21, 28 respectively are traversed, substantially as in a phantom circuit, by the biasing current which flows in the same direction in both conductors of the same pair, whereby the symmetry is magnified considerably. The line section extending from the one or the other end of the whole line to the next pair of negative resistances 35, 36 and 31, 38 or 43, 44 and 45, 46 respectively is suitably equalized to one half of the length of the other line sections for instance 35, 39 36, 40. In this manner an easy connection of lines may be effected.

Fig. 3 represents an arrangement for supplying the biasing current by a separate conductor. To the terminals of the negative resistances 48, 49 arranged symmetrically in the two conductors 51, 58 of a two-wire circuit, are connected the chokes 50, 5| which connect the said two conductors to one another. From a third conductor 41' the biasing current is supplied to the negative resistances through the said chokes. The capacities 53-56 serve to prevent a flow of direct current through the conductors 51, 58. On

the other hand, a capacity 52 is arranged to provide a short circuit for any signal currents which may flow through the chokes 5|], 5|.

Instead of a separate line such as described above, a phantom circuit may be employed as a common supply circuit for a plurality of lines. In all cases it is preferable to employ side circuits at a considerable distance from one another in the bunch, in view of using a high input voltage. To cause the biasing current to flow through the conductor in the same direction, it is also possible to shunt all conductors with respect to the biasing current by cross resistances or equivalent elements and to employ a common return conductor. The latter may be a separate conductor, or the cable sheathing, or the earth, or seawater.

In many cases it is not possible to conduct a direct current as a biasing current along the lines A resistances orover those parts :ofthe line which.

on account of-interference from foreign sources, such as power currents. In such cases it is preferable lto bloclr the line or sectionsof the line p by transformers. fhFor. other reasons aswell, for

instance when using amplifiers or capacitive couplings in the line, ,a direct currentflow can be prevented.

According to" one, feature or embodiment of [our invention an alternating current is. corfducted to the points at which there are negative do notpermitaflow of direct currentgand is rectified before being: supplied to the "negative resistances. Thealternating current source may I belocated at the endof the line or of the subsection of the line, 'orconnected to separate conductors provided: for supplying the biasing curwrent. PreferablyQthe rectificationis-eflected by contactdevices, forflinstance dry rectiflersor in, ,any other well known or approved mannen For this purpose we may use negative resistances of p the same character. as those provided for reduc ing the attenuation of the line.. an example of'such anarrangement.

Fig. 4 shows 1 -At 53 we haveindicateda longdistance line,

for instance a submarine cable havingonly one conductor, the return conductor-being replaced by;sea-water.- At 8|, Bland ",lflrespectively,

we have indicated. the terminal transformers to the primary windings ofwhich standard .or approved apparatus, for instance any well-known telegraphy apparatus, are. connected. .The line .59 1 is subdividedinto; several sections, eachhaving a repeaterstation formed by connections with negativeresistances such as the one, indicated at 'lLmLet, us. assume that thetelegraph cur- .rent has a frequency at the lower limit of audio-freqi' ency,and that for biasing thev negw filter 65, capacity 15, negativeresistancelkcaa ti ve resistances .there is superposed on the line 59 an alternating currentwhich-has a frequency below :the audio-frequency band. In the station 60 the telegraph current flows through the pacity. I6 and rfilterwaflback to the line section between 60 and 6|; The .filter 64 does'not permit passage of the telegraph current but of the superposedtbiasing current, so that the latter flows through the primary winding Ill ofa transformer, the secondary winding of which is connected to a rectifier 12; The rectified alternating, current is supplied over the chokes 11;" to the negative resistance II and acts as abiasing current. The capacity: 13 servesasa short circuit for audio-frequency currents coming over 11,18. Ina parallel lbranch, thealternating current from the filter 64 flows through the filter l9 and furthermore to the line 59;: The filters 64 and 19 do not permit the passageof audio-frequency. currents and are earthed by theconductors 66, 68. The superposed current for biasing purposes ,might also be in the range of upperaudio-frequencies.

According to a further feature of our inven- -tion, in linescontaining negative resistances for reducing the energy losses, means are provided by which the negative resistances can be controlled or switched'in or out. This arrangement is particularly advisable in the case of long lines. These means can be adjusted manually or automatically and located at the termlnalsof the lines or in subsections of the lines. In the latter case a remote control is desirable." r

In the simplest embodiment of ourinvention, the biasing current flowing through the line is controlled for all negative resistances at the I terminals of the lineor at any other .pointof the line. This permits acommon variation of the attenuation to be effected for the whole line. Regulation may be effected by varying thevoltage of the biasing current or-by yarying the resistanceof a branch .of the biasing circuitpnot traversed by the signal current. Foninstance, Y

as indicated in Fig. 2, theconnection ,of the. batteries 33 and 34 i with the coils of the respective transformers. may be adjustable, the arrows being theconventional representation ofcontrollers or slides which can be moved to different points: of thelsaidcoils. v When the line issubdivlded into several sections and a separate biasing source is 1 provided for every section, the same arrange ments can be made. Another possibility consists .in apportioning or attaching'to every 'negative resistance the value of which islto' be controlled,

or. to a groupof such resistances, a special operatlng device, for instance a selectiveswitch-,: by which it, is possible-to effect a variation of the resistance values, for example a switching in or out (Of :the resistances By such an operatingdevice 2. parallel" resistances can hex-switched in -or out in steps, for instancethebiasing current or the signal currentmay be conducted over this parallel circuit. The variation .of the negative reisistances can be aiso efl'ected in a continuous mannerwforc instance by influencing continuously changeable positive resistances connected to the'negative resistances. The said regulatingdevices can be controlled in any-well-khown :manner from the terminals of the. line, or from supervisory'stations atother points ;of the line, or in dependence upon" the attenuation of the line; According to a further feature of our invention, we may employ the biasing current itself forthe remote controlof the regulating device, by transmitting impulses for a short time by means of this current, .whe're" by for instance a selective switch is controlled. 1 Using alternating current as the biasing current for the negative resistances rec ifledat the points where negative resistances are located, switching apparatus can be controlled selectively fby varying the frequency of the alternatingcurrent in a well-known manner. 'It is also wi hin the scope of our invention to employ for the'reniote con- 'trol, separate lines or channels over which the control of 'theregulating dvices is eilected by alternating or direct current.

i What weclaim isz" j N .1. A signaling system comprising lines for signal transmission, said lines extending from a transmitting station to a receiving station, negative resistances connected in these lines at diiferent distances from the endsjof the lines, for reducing the loss of signalenergy, and especial line extending lengthwise oi' the signaling systein and connected .with aplurality' of said signal lines for supplying currents to bias the negative resistances.

2. A cable circuit, comprising lines for signal resistances connected in these lines at difl'erent distances from the ends of the lines, for reducing theloss of signal energy, a,source of bias current, a separate conductor for supplying said bias current to said negative resistances, and separate means for the return of the bias current to its source.

3. A cable circuit comprising lines for signal transmission, said lines extending from a trans,- mitting station to a receiving station. negative transmission, said lines extending from a transmitting station to a receiving station, negative resistances connected in linesat different distancesfrom the endsoi the lines, .flirnireglucing the loss of signal energyj'a source oi'biascurrent, and a two-wire circuit ior'supplying said bias current to said negative resistances, the twowires of said circuit within the cable being well separated from each other electrically.

4. A signaling system comprising a signal line extending from a transmitting station to a receiving station, negative resistances connected in said line at different distances from its ends, for reducing the loss of signal energy, a separate line for supplying biasing current to said negative resistances, filters interposed between the said biasing current line andthe signal line to block the signal currents, and devices located in the signal line on either side of each negative resistance, to block the biasing current.

5. A signaling system comprising a signal line extending from a transmitting station to a receiving station, negative resistances connected in said line at different distances from its ends, for reducing the loss of signal energy, and a separate line for supplying biasing current to said negative resistances, each side of a negative resistance being connected with the same-conductor of said separate line.

6. A signaling system comprising two signal lines each composed of two conductors, negative resistances connected in said conductors, and a separate current supply circuit for biasing the said negative resistances, the two conductors of one signal line being connected in parallel for leading the biasing current in the one direction, and the two conductors of the other signal line being connected in parallel for leading the biasing 'current in the other direction.

7. A signaling system comprising a cable containing two signal lines each composed of two conductors and well separated electrically from the other line, the two conductors of the same line being connected in parallel, negative resistances connected in said lines, and means for supplying biasing currents to said negative resistances, said biasing means being connected to each of said four conductors.

8..A signaling system comprising a signal line composed of two conductors, negative resistances connected in saidconductors at corresponding points thereof, cross-connections between said conductors to connect them in parallel at the two terminals of said negative resistances, and a separate line, connected with said cross-connections, for supplying biasing current to said negative resistances.

9. A' signaling system comprising a signal line, negative resistances in said line, a source of current for biasing said negative resistances, and a single controller, connected in series with a pluralityoi said resistances for varying the voltage of "said' biasing current in such plurality of resistances.

10. A signaling system comprising a signal line, negative resistances in said line, a source of current in circuit with said negative resistances for biasing the latter, and a single controller, connected in series with all the resistances in said circuit, for varying the resistance of the circuit through which said biasing current flows through all of said resistances. A

11. A signaling system comprising a plurality of independent electrical circuits for signal transmission, each circuit having conductors extending from a transmitting station to a receiving station, negative resistances connected inthese conductors for reducing the loss of signal energy, and means for supplying currents to bias the negative resistances, saidmeans including auxiliary conducting means connected between said conductors and connected to a source of current to form an electrical circuit through said resistances and substantially coextensive with said system.

12. A signaling system comprising atplurality of independent electricalcircuits fqr sigjnal transmission, each circuit having conductors extending from. a transmitting station to a receiving station, negative resistances connected in these conductors for reducing the-loss oi;sig'nal energy,

and means for supplying cur'rentsl' to bias the negative resistances, said means including current supply means,- auxiliary currentlconducting" conductors for reducing the loss oi signal energy, 7

and means for supplying currents to bias the negative resistances, said means including unidirectional current supply means connected to said conductors for passing the biasing current at least through parts of said conductors and to form electrical circuits through said resistances and substantially coextensive with said system.

14. A signaling system comprising a plurality of independent electrical circuits tor transmitting separate signals between stations,- each circuit having a conductor with ,negative gesistances connected therein to redu'cefthe lossoi vsignal en ergy, and means to supply current to bias said resistances, said means comprising a source of bias current and means connecting said source with each of said independent circuits.

MARTIN BAESECKE.

HANS MAYER.

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