US2207531A - Four-wire signaling circuits - Google Patents

Description

July 9 1940 N. BoTsFoRD FUR-WIRE SIGNALING' CIRCUITS Filed Nov. 5, 1938 2 Sheets-Sheet 2 FOUR -W/RE C/RCl/l T Faun-WIRE c/Rcu/r /IV VE /V TOR N QQQQQIO n l2 u lo Il 8 g A TTOR/VE V Patented July 9, 1940 UNIT-ED 'STATES 2,207,531 .e x l l FOUR-WIREr SIGNALING jerectil''rs f Nelson Botsford, Rutherford, N. J., assignor to Bell Telephone Laboratories, Incorporated, New York, N. Y., a corporation of N ew York. f

vApplication November 5, 1938, SeriallvNo. 239,005

1 Claim.

i' This invention relates to signaling circuits embodying hybrid coils and more Aparticularly to hybrid coil arrangements for associating two` wire circuits with four-wire circuits.

He'retofore hybrid coil arrangements have been used in signaling circuits for connecting a two-wirel circuit with a `four-wire circuit. Certain'ofsuch arrangements are disclosed in the patent to H. Nyquist No. 1,504,135, granted August v5, 1924. The present invention is an improvement over the Nyquisty circuit in that provisionis made for minimizing or obviating the effects of .longitudinal currents induced in the two-wire circuit. The eifects of these currents are blocked vfrom the four-wire circuit thereby precluding interference therein with the transmission of v signaling currents.

It is an object of the present invention to provide a Ahybrid coil arrangement for coupling a two-wire circuit to a four-wire circuit in a manner su'ch that the effects of longitudinal cur. rents in the two-wire circuit are canceled and' therefore do not appear in the four-wire circuits. .In'a preferred embodiment the invention comi '.5 prisesra pair of multiwinding inductance coils,

two windings of the one connected in series with twol windings of the other and both pairs applied to a two-wire circuit. A mid-point of these windings is connected to ground. Accordingly, o longitudinal currents induced in the two-wire circuitv flow to ground in opposite directions in each of the two windings on the saine core. This causes the flux due to the longitudinal current in one winding to oppose the flux due to the longitudinal current in the other winding on the same core. Consequently, the effects of the longitudinal currents are calceled and therefore do not reach` the four-wire circuit.

v`The invention will be more readily understood from the following description taken together with the accompanying drawings in which: y

Fig. l is a circuit diagram showing a preferred embodiment of the invention;

Fig 2 is a circuit diagram illustrating a modi-v fication oi Fig. 1;

Fig. 3 is a circuit diagram showing an alternate form of the invention; and

Fig. 4 is a circuit diagram showing the invention used in a signaling system for deriving phantom'circuits.

In the drawings the same reference numerals are' employed to designate identical elements appearing in the several gures.

Fig. 1 shows a two-wire two-way transmission circuit L associated with transmission paths L1 and L2 through a hybrid coil I3.l The paths L 1 and L2 may: constitute the four wires of a four` wire circuit, 'or those leading to a four-wire repeater circuit, Butone end of the four-,wire circuit is shown. Afor Lthe reason that the other end 5 is identical therewithfand is well understood in theart.;"fA n The hybridrcoil yI 3 comprises individual coils I4 and I4a,.eachcoil including tsix windings, I6, n, la and is, which are preferabiy wound as a 1 quad although wound in layers would serve, equally as well'fas long as they are well balancedand closely coupled and a pair of seriallyconnected. windings 2:0 and2I.` The windings I8 and I9 on coil I4 are connected in series and the windings Iiiaand .I 9c on coil I 4a are also connected in series. 'In addition, the windings I 8 and.

I 9 are connected in series with the windings I 8a and I9a, aiicbthe terminals 9 and I2 of the respectivewindings 19a and I9 are applied to a- 20 well-known balancing network N. It is understood that .thecoils I4`and Illa are provided withy cores ,of` suitable magnetic material on whichthe various windings are wound. p

The winding I6 oflcoil I4 is connected in series 25 with theA winding Ilia on coil I 4a, the latter winding being connectedin `series with the winding I "la: on: the4 same coil. v'I'he winding I'Ict is also connected in serieswith the winding I 1 on the coil I4. yThe terminals 5 and 8 of the respective 3 windings I6 andv I'I are applied to the circuit L. 'I hus the arrangements of the windings I6 and I'I on coil I4'r and of the windingsy I 6a and Ila on coil. Illa are such that the windings onthe same core are connected in a series-aiding relation- 35 ship. The ilow of signaling current in the wind-A ings of each coil .is in ythe same direction and is indicated by the solid arrows associated there! with.

The'mid-poiutofV thewindings I6a and I'Ia is` 4U connected by. .a lead122 to ground 23. `'Ihis also serves to "connectto groundthe mid-point of the serially-connected windings I6, I6a, I'Ia and IIl.

`The serially-connected windings 20 and 2I on coil I4 serve to couple windings I6, Il, I8 and I9 to path L1 4while the serially-connected windings 2Ua'and2la on `coil I4a serve to couple windings IGa, Ila, I8a and I9a to path L2. It is understood thatfthe impedance of the circuitvL, 50

balancing network N, and paths L1 and Lz may be so related by the coils I4 and I4a that signaling energy transfer may be accomplished in desired proportions.v As such transfer is well under' stood in the art,- a further discussion-thereof@ is deemed unnecessary here but reference is made to the patent to H. Nyquist, supra.

In Fig. 1, the numerals I through I2 indicating the winding terminals serve to designate the polarity thereof, that is, current ilowing in any winding from an even to an odd numbered terminal produces ux in the core associated therewith in one direction while current flowing in any winding from an odd to an even numbered terminal produces iiux in the core associated therewith in an opposite direction. This is also true with regard to Figs. 2, 3 and 4 in which the respective i-f windings of the hydbrid coils are similarly desig-K. nated as in Fig. 1 and which will Vbe hereinafter described.

The arrangement shown 1n Fig. 1 is particularly adaptable for use in toll`circuits in iwhichv1 it is desired that current from a battery 281e-,k

cated at a toll oiiice be transmitted over the circuit L to a subscriber connected to the'terminal thereof, not shown. In the event of longitudinal or noise currents being induced in the circuit L and transmitted toward the toll oiiice, these currents would ilow to ground 23 through the windings IB, Ia, IIa and I1 in the directions indicated by the dotted arrows. It will be observed that the noise currents flow inopposite directions through the windings I6 and II of the coil I4 and also in opposite directions 4through the windings IBa and. I'Ia ofthe coil I4a. Hence, the flux produced inthe cores of the coils I4 and I4a and due to the rnoise currents owing in the respective windings will be in opposition. Consequently, the

effects of the noise currents willbe canceled inl the coils I4 and I4a, and will not enter either path L: or path Lz.

Thef arrangement of Fig. 1 provides for a high loss from path L1 to path L?. for the reason that loss therebetween depends solely on the equality of the windings I6, I1 and I8, I9 on coil I4 and of the windings Ia, Ila and IBa, I9a on coil I4a, assuming that the impedance of the network N equals that of .the circuit L. These windings on the individual` coils I4 and I4a are inherently excellent since they are very closely associated, being wound at the same time as a quad. While winding as a quad is preferable, it is not necessarily limited thereto as pointed out hereinbefore.

Longitudinal currents on the side of the balancing network N are normally negligible and usually there is no need of grounding the midpoint of windings I8, I9, I8a and |911. Consequently, windings I8 and I9 on coil I4 and windings l8a and I9a on coil I4a may be wound on the respective coils as a single winding. This does not affect the balance oi the circuit L although itmay lower the loss from the path L1 to the path L2 by placing less winding capacity across the network N than is placed across the circuit L. The high loss from the path L1 to the path L2 may then be brought back to a desirable level by placing a condenser 26 of proper capacity across the network N in Fig. 1. Thus the condenser 28 servesto render the effective winding capacity across the network N equal to the effective winding capacity across the circuit L.

Fig. 2 is identical with Fig. 1 except the winding I9 on coil I4 is connected in series wth the serially-connected windings I8a and I9a on coil I4a while the latter are also connected in series with the winding I8 on coil I4. The terminals 9 and I?. of the respective windings I8 and I9 are applied to the network N. Thus the connections of the windings applied to the network N are equivalent from a capacity standpoint to the connection of the windings I6, I1, Ilia and IIa applied to the circuit L. This arrangement obviates the condenser 26 of Fig. 1.

The arrangement of Fig. 2 is particularly adaptable for use in the derivation of phantom circuits as illustrated in Fig. 4. Referring to the latter, signaling currents flow in the physical circuits and 3| and the respective hybrid coil sets vA and C in the directions indicated by the solid arrows. In this connection it will be observed that the flow of signaling current in the windings oieach coil I4 and I4a comprising the respective .hybrid coil setsA and C is in the same direction. Transfer of signaling energy between the two- 1 wire circuits 30 and 3I and the four-wire circuits "lassocia'ted therewithy is effected in the manner "mentioned above relative to Fig. 1.

Phantom currents` flow in the physical circuits I 3l] and 3|, the hybrid coil sets A, B, and C, and the'connetions therebetween in the directions indicated by thedot-dash arrows. These currents flow ,in opposite directions in the windings of the ,coilsz I4 and [4a comprising the hybrid coil sets A and C. `The Aflux due` to these currents will be in opposition in the cores associated with the respective coils I4fand, I4al and the effects of the phantom currents will therefore be canceled in the respective hybrid coil Asets A and C. Consequently, lthe effects of the phantom currents will not reachfthe, four-wire circuit associated with thehybr-id coilsets A -and C. However, in the windingsof rthe coils I4 and I4a comprising the hybridu coilset B, phantom currents iiow in the same direction.- TheV flux due to this current in the hybrid'coil .set B, will bein an aiding relationship` and the effects of `the phantom currents will be thereforetransferred to the fourwire,circuituassociated with the hybrid coil set B. The transfer of ,this energy between the twowire and .the four-wire circuits is eiected in the proportionmentioned above in connection with Figi. .l Noise or 4longitudinal currents induced in the two- wire circuits 30 and 3| in Fig. 4 ow therein and in the windings of the vhybrid coil set A, B and C to groundl 32 connected to the mid-point of the windings of the coils I4 and Illa. comprising the `hybrid coil set B in the directions indicated bythe dotted arrows in a manner siminar to that for the ow of, noisecurrents in Fig. l as explained above. .Thus the noise currents ilow in opposite directions in the windings of each of the coils I4 and I4a comprising the hybrid coil sets A, Band C. As the flux ldue to noise currents is also in opposition in the same cores associated with the respective coils I4.and Ida., the effects of noise currents will be canceled and will therefore not reach any of the four-wire circuits.

It is to be understood that the organization of Fig. 1 may also be used for the derivation of phantom circuits in the manner aforedescribed with regard to Fig.4 4.

Fig. 3 is generally similar to Fig. 1. In Fig. 3 winding I6 on coil I4 is connected in series with winding Ila on coil I4a. The latter Winding is connected in series with Winding I1 on coil I4 and winding I1 is-connected in series with winding Ia on coil I4a. The terminals 5 and 8 of the respective kwindings `I6 and I6a are applied to the circuit L. Thus, the windings I6 and I1, and also Ilia and I la ,are arranged in a series-aiding relationship on the respective cores. The midpoint of the windings on the coils I4 and I4a is connected by a lead 24 to ground 25. The serially-connected windings I8 and I9 on coil I4 are connected in series with the serially-connected windings i811 and lSa on coil Ma. The terminals i2 and I2 of the respective windings i9 and Ia are applied to the network N.

In Fig. 3 signaling currents flow in the two- Wire circuit L and the windings of the coils i 4 and idc in the same direction as indicated by the solid arrows. The transfer of signaling energy between the two-wire and the four-wire circuits is accomplished as mentioned in connection with Fig. l. Noise or longitudinal currents induced in the two-wire circuit L and owing therein and in the windings of the coils I4 and Ma to ground 25 are indicated in Fig. 3 by dotted arrows. It is seen that these noise currents ilow in oppositedirections in the windings IS and il and also in the windings ita and lla. The ux due to these currents is in opposition in the same cores and the eiects of the noise currents will be canceled. Consequently, the effects of the noise currents will not reach the four-wire circuit. The hybrid coil according to Fig. 3 may also be used in the derivation of phantom circuits in a .manner sirnilar to that illustrated in Fig. 4. This arrangement also includes the condenser 26 whose function was mentioned above relative to Fig. 1. The use of this condenser may be avoided by connecting the windings applied to the network N in such manner that the latter are equivalent from a capacity standpoint to the connection of the windings applied to the circuit L, as mentioned above with regard to Fig. 2.

It is to be understood that the invention is not limited to the precise details of the circuits illustrated and described for it is apparent that numerous modifications thereof could be made without departing from the spirit of the invention, the scope of which is to be determined by the appended claim.

What is claimed is:

A hybrid apparatus for associating a two-wire circuit, a four-wire circuit and a balancing network, said apparatus comprising a pair of multiwinding coils, a irst pair of windings on a first coil connected in series, a first pair of windings on a second coil connected in series, the two first irs of serially-connected windings connected in and arranged so that one winding of .each thereof is applied to the balancing network, a second pair oz windings on said rst coil con` neoted in series, a second pair of windings on said second coil connected in series with the seriallyconnected second pair of windings on said first coil, each oi' the second pairs of windings disposed in a series-aiding relationship, the serially-connected second pairs of windings arranged so that the second pair of windings on said second coil is connected to thetwo-wire circuit, the iirst and second pairs of windings on each of said coils applied thereto as a quad, grounding means, a lead connecting the grounding means to a midpoint of the serially-connected second pairs of windings so that longitudinal currents induced in the two-wire circuit iiow in opposite directions in each winding of the second pairs of windings thereby canceling the eiects thereof in each of said coils, a third pair of serially-connected windings on each of said coils for coupling of the first and second pairs of windings thereon to the fourwire circuit, and a capacity in bridge of the network for rendering the effective capacity of the windings applied thereto substantially equal to the eiective capacity of the windings applied to the two-wire circuit.

NELSON BOTSFORD.

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