US2147690A - Telegraph repeater - Google Patents

Description

Feb. 2v1, 1939. w, w. CRAMER' ET AL TELEGRAPH REPEATER Filed Aug. 30, 1935 2 Sheets-Sheet 2 G. C. C 0MM/NGS A TTORNEV Patented Feb. 21, 1939 PATENT OFFICE 2,147,690 TELEGRAPH REPEATER Walter W. Cramer, Rutherford, and George C. Cummings, Orange, N. J., assignors to Bell Telephone Laboratories,

Incorporated, New

York, N. Y., a corporation of New York Application August so, 1935, serial No. 38,528

21 Claims.

'This invention relates to telegraph repeaters, and more particularly, to telegraph repeaters of the balanced type in which one relay must be held inoperative While another relay transmits signal impulses through the Winding of the inactive relay.

An object of the invention is to prevent the inactive relay from being operated by line discharges when the active relay is operating.

Another object is to provide a repeater of simple design which may be effectively operated in conjunction with any one of a plurality of comparatively high capacity lines, such as long subscribers loop circuits. o Another object of the invention is to arrange for the counteraction of line surges through a repeater relay Without the necessity of increasing the line current beyond that used in ordinary practice.

The present day tendency is to interconnect telegraph subscribers through svvitchboards which are equipped with repeaters. Therten'dency is, furthermore, to use longer and longer subscribers loop circuits and to include the conductors for such loops in cables so that their capacity to ground, as Well as their mutual capacity, becomes quite appreciable. The discharge surges from the 'e line, consequently, are becoming more and more pronounced and it is becoming necessary to provide against their effect upon the relay operations.

When ,a marking potential is applied to a high capacity line, the so-called marking surge acts to charge the line to a given potential, both with respect to ground and with respect to the return conductor. This surge is in a direction such that the inactive relay is held to marking. When a spacing potential is applied to the line through the line Winding of the inactive relay, a surge in the opposite direction or spacing surge takes place to discharge the line with respect to ground. This surge tends to operate the inactive relay to spacing, which, of course, is not desired. In certain types of repeater circuits these conditions are reversed.

In accordance With a feature of the invention, a uni-lateral device is connected in circuit With the inactive relay in such a manner that it will prevent the relay from kicking off during the spacing surge referred to above.

In accordance with a further feature of the invention, the unilateral device is'associated With an impedance to form an asymmetric multiple network which provides two paths, one forvthe normal current and one for a transient current.

be the surge impulse or a 'counter-eifective transient impulse, Y l o Y The invention Will now Abe described as y'applied in 'diler'ent manners to a typical telegraph vrepeater circuit and reference Will be made to the attahed drawings, ih 'Whichv Figs. 1, 2, and 3 show a half 'duplex4 repeater of the balanced ltype in which the unidirectional device is associated With the lille Winding Of the inactive relay in different manners, and A Figs. 4 and 5 show the device associated with the balancing 'v's'rinding of the inactive relay. In Figs. 1 to 4, inclusive, the invention is illustrated inl connection with a,Y subscribers loop, Whereas in Fig. 5 the invention is illustrated in connection with a composite telephone line.

In`the drawings, only enoughy ofnthe repeater station is 'shown inthe various iguresoto facilit'ate the'understandng of the principles and operatioris of the invention. Thus, in each repeater only those parts are shown which cooperate with one line or loop circuit, it being understood that for the purposes of thelinvention the connections to the other line circuit may be madein'any desirable manner, and may be madevin the same manner as those illustrated. l L n The embodimentsutoovvhich the rinvention will be applied,` while `being preferred, are merely given as examples; other Ways or rmodifications in which the advantages and features of the invention may be utilized will be obvious to one skilled in this art. v Y

In orderv thatuthe operation of the invention may be clearly understood, theline circuit shown each of the circuit arrangementsl in the drawings vvill be assumed to be of considerable length and to be composed practicallyentirely of va pair v of cable (on'ducjrsk enclosed by a lead sheath. The line circuit will thus have appreciable mutual, distributed eapacitanee between thel two conductor'sand also'vv grounded distributed capacitance between each conductor and the cable sheath. These capacitances are diagrammatically illustrated in the drawings by dotted condensers.

Referring now particularly to Fig. 1, the send-- ing relay |0| of repeater R is actuated in any suitable manner and transmits positive and negative impulses through the upper or line winding of receiving relay |02 and over the line circuit I 05, |06 to actuate the distant subscribers station S, it being a requirement of the circuit that the armature of receiving relay |02 be held Vfirmly on its right-hand or marking contact while pulses are being transmitted from sending relay |0|. The distributed capacitance between line conductor |05 and ground is represented by condensers ||0 and and between conductor 06 and ground by condensers ||2 and H3, and the mutual distributed capacitance between conductors |05 and |00 is represented by condensers ||4 and H5.

The subscribers station S may be equipped with standard teletypewriter apparatus and thus will have a receiving winding responsive to incoming signals'for operation of the translating or recording device, and transmitting or distributor contacts responsive to actuation of the keyboard to transmit impulses into the line circuit.

VWith the armature of relay |0| on its righthand contact, as shown, a marking impulse is sent over the line to actuate receiving apparatus at station S. This marking circuit is traced from positive battery through the right-hand contacts of relay |09, through the upper winding of relay |02, resistance |03, conductor |05, station S, conductor |00, to negative battery through variable resistance |08. A unidirectional device |04 is connected in parallel with the upper winding Vof Y relay |02 and resistance |03 but is poled in a direction so that very little or no current flows through it during the marking impulse. Another circuit involving the lower winding of relay |02 is traced from positive battery through the righthand contacts of relay |0| through the lower winding of relay |02 to ground through balancing network H0. With the same number of turns in the windings of relay |02, the current in the lower winding is about one-half of that in the upper winding, and tends during marking condition to move the armature to spacing.

When .sending relay |0| closes its left-hand contacts, negative battery is connected to negative battery over the line circuit described above and the current through the lower winding of relay |02 is reversed to hold the armature to marking as the line current becomes zero. However, the'line capacities ||0 and will now be charged to a negative Apotential with respect to ground and the capacities ||4 and ||5 will discharge throughVV the line winding of relay |02. Thisy transient currentin the upper winding of relay |02 would tend to operate the relay to break its right-hand contacts were it not for the fact that the unidirectional device 00 is connected in such a way thatthe major part of the transient current 'is shunted through it instead of traversing the upper winding of relay |02 and resistance |03. By this means, the reversed flux which would ordinarily be generated by the upper winding of relay |02 is insufficient to overpower that of the lower winding and cause the armature of relay |02 to leave its right-hand or marking contact.

When the line circuits described above are again closed to marking potential, condensers I0, H4 and H5 will again be charged to positive potential and the charging current will pass with its full strength through the upper winding of relay |02. Ihis causes a transient condition in relay |02 during which the upper winding is more powerful than the lower winding. However, the additional ux generated by this transient current is in a direction to hold the armature relay |02 more rmly on its right-hand or marking contact and no diiiculty is experienced upon the charge of the line capacity on the marking impulse.

Fig. 2 shows an arrangement Very similar in its action to that of Fig. 1 except that a unidirectional impedance network consisting of resistance 220 and unidirectional device 204, is inserted in series with the line circuit instead of being connected as a shunt path for the upper winding of the receiving relay as shown in Fig. 1.

In Fig. 2, the transmitting circuit for the marking impulse is traced from positive battery through the right-hand cont-acts of sending relay 20|, the upper winding of relay 202, resistance 203, resistance 220 in parallel with unidirectional device 204, line conductor 205, station S, line conductor 206, to negative battery through variable resistance 208. When this condition was first established, the line current was in a direction to meet a low resistance path through unidirectional device 204 and a heavy transient current, due to the reversal of charges on condensers 2|0 and 2|| and to charging of condensers 2|4 and 2|5 which represent the line distributed capacity, traversed the upper winding of relay 202 in a direction to cause the latter relay to hold its right-hand contacts rmly closed. When sendingrelay 20| reverses the direction of current in the line, however, the unidirectional device 204 presents a large resistance to the line current and the charging current of condensers 2|0, 2|I, 2|4 and 2|5, as well as the spacing impulse, is forced to traverse resistance 220 which reduces the current surge suiciently to prevent relay 202 from breaking its right-hand or marking contacts'.

Referring now to Fig. 3, a circuit is shown which combines some of the features of the circuits shown in Figs. 1 and 2. Inthis case, two l,

its right-hand or marking contacts, positive battery is connected through the upper winding of relay 302, unidirectional device 304, line conductor 305, station S, to negative battery over line conductor 300. Unidirectional device 304 is connected in such a way that itsY resistance is low to the current in the circuit described above. Unidirectional device 308 in series with resistance 303 is connected in parallel with the upper Winding of relay 302 and unidirectional device' 304, but device 308 is poled inthe opposite direction to device 304 and the circuit Velement comprising unidirectional device 308 and resistance S03 is of sufficiently high impedance during the marking impulse to have a negligible shunting effect on the upper winding of relay 302. As in the previous cases a parallel circuit is provided to energize the lower, balancing winding of receiving relay 302, this circuit being traced from positive battery through the right-hand contacts of relay 30|, through the lower winding of Vrelay 302 to ground through balancing network 3| 6. As in the previous cases, the transient current due to the marking charge of line capacities 3|0, 3| l, 3M and SI5 traverses the upper winding of relay 302 but tends to keep the armature of relay 302 firmly against its right-hand contact,

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When relay 301 closes its left-hand contacts to ksend a spacing charge which is in the opposite direction to :the marking charge, unidirectional device 304 effectively .prevents the charging current of condensers 3:10, 311, 314 and 315 from traversing the upper winding of relay 302, while unidirectional device 308 and resistance 303 provide a low resistance parallel path so that the spacing impulse is transmitted to station S.

nbecause it removes the unidirectional device from the line circuit. In this case, when sending relay 401 closes its right-hand contacts, positive battery is connected through the upper windings of vreceiving relay 402 and break relay 403 in series, through variable resistance 404, line conductor 405, substation S, to negative battery over line conductor 405. When the condensers 410, 411, 414 .and 415 are charged to this condition, the transient current through the line windings of relays 402 and 403 keeps the armatures of these 1^elays on their right-hand or marking contacts. A parallel circuit is traced from positive battery through the right-hand contacts of relay 401, lower windings of relays 402 and 403, resistance-408, to ground through resistance 416. A network consisting of condenser 418, resistance 419, and unidirectional device 41'.' is also connected in this circuit but due to the poling of unidirectional device 411, no appreciable current iiowsin it.

When relay 501 closes its left-hand contacts to send a spacing impulse, line condensers 410, 411, 414 and 415 charge through the upper windings of relays 402 and 403, sending a transient wave through these relays, which would ordinarily cause them to break their right-hand or marking contacts. In this case, however, the current through the lower windings of relays 402 and 403 and the balancing network finds a low impedance path through unidirectional device 4i? and the large condenser 418. A transient current, therefore, flows through the lower windings oi relays 402 and 403 which effectively neutralizes the transient in the upper windings and prevents these relays from opening their righthand contacts. Resistance 4 I 9 is provided to discharge condenser 418 after the circuit has reached a steady state.

In Fig. 5, an arrangement is shown for applying the features of the invention to a composite telephone and telegraph circuit. In this case, as in Fig. 4, a unidirectional device is connected in the local circuit for the balancing network of the receiving relay to provide balancing transients during spacing impulses without introducing transmission losses. When transmitting relay 501 is actuated to marking, it closes its left-hand contacts and negative battery is connected through the upper winding of receiving relay 502, through the compositing set 553,

over line conductor 505, through compositing set 50i', the upper winding of receiving relay 503, to negative battery through the left-hand contacts oi relay 500. Thus, no current iiows in the line circuit during marking. At the same time, a parallel circuit is closed from negative battery irough the left-hand contacts of relay 501 through the lower winding of relay 502, and the duplex balancingcircuitto ground. The cur- Arent in this circuit vholcls relay 502 in marking position.

The balancing circuit in this instance may comprise the usual line balancing resistances 511 and 514 and capacity 513 and also a separate balancing unit V504 for balancing the impedance of the compositing set 503 in the line circuit.

Unidirectional device 512 is connected in parallel with the llower winding of relay 502 and resistance 511 .in such a way that when relay 501 `operates to spacing, condenser 513 will be charged ,to a positive potential with respect to ground through the unidirectional device 512 and the current through the lower winding of relay 502 which tends to operate the relay to spacing will be of very small value. Line condenser 556 then will also be charged to positive potential, but the line current which traverses the upper winding of relay 502 is in a direction to cause the relay to remain rrnly upon its righthand or marking contacts.

When relay 501 closes its left-hand contacts to transmit a marking impulse, line capacity 505 is charged to a negative potential through the upper windingof relay 502. In this case, however, the transient current in the upper Winding or" relay 552 is in a direction to tend to operate relay to spacing; however, condenser 513 now charges in a direction through the lower winding of relay 502 to hold the relay in marking position. A heavy transient current is therefore generated in the lower winding of Arelay 502 which opposes the transient in the upper winding and eectively prevents relay 502 from opening its right-hand contacts.

In a similar manner, relay 50S may transmit marking and spacing impulses to receiving relay 552 without causing relay-508 to open its leftcontacts because of the similar circuit arrangement involving balancing network 510, unidirectional device 516, condenser 51'1, and resistance 558. When relay 509 is operated to spacing, the line winding o relay 502 will oppose the biasing winding and the line current Will be sufficient to operate the relay to spacing.

For a complete system extending from the subscribers station S in the various figures to ,another similar subscribers station, the entire system shown in the drawings, except relays 101 and 102 in Fig. l and corresponding relays in the other figures, may be duplicated. Thus, for example in Fig. l, the contacts S and M of relay 102 would constitute sending contacts for the other line circuit corresponding to the contacts of relay 101; one winding of relay 101 would be connected to the incoming line and the other winding would be included in a biasing circuit similar to that including the lower winding of relay 152 and the network IIB. In Fig. 5, the windings or relay 501 may be connected like those of relay 50S, and the contacts of relay 502 like those oi relay 509 for operation with a line similar to line 555.

W hat is claimed is:

l. A polarized signal relay having two windings for producing opposed fluxes resulting in an operating ilux, a signaling circuit including a line circuit and balancing circuit means, said windings being connected in said signaling circuit, and unidirectional circuit means and impedance means in multiple relation and associated with one of said windings to prevent a discharge of said signaling circuit from reversing the direction ofsaid .operating flux.

. balancing Awindings respectively, signaling means connected to thel other side of said windings for alternately charging and discharging said signaling circuit, and unidirectional circuit means and impedance means in multiple relation and connected to one of said windings to prevent said charging and discharging of the signaling circuit from operating the relay armature by proportioning the discharging currents through said Win-dings without substantially affecting the charging currents therethrough.

3. A polarized signal relay having a line wind-f ing and a second Winding, a signaling circuit including a line circuit and balancing circuit means,

said windings being included in said signaling circuit, signaling means for oppositely energizing said win-dings to produce a resultant operating flux during sending of a current impulse and for energizing said second winding to produce a holding flux in the same direction as the operating ux during sending of a no-current impulse, asymmetric circuit means including a unilateral device and a by-path therefor connected to one of said windings to cause during a no-current impulse the iluX produced by said second winding to be larger than the uX produced by a surge current from the line circuit through said line winding.

4. A polar signaling relay, a line circuit including a Winding of said relay, a balancing circuit including another winding of said relay, signal transmitting means connected to apply alternating potentials of opposite polarities simultaneously to both of said circuits thereby producing an alternating current through one of said windings, and a multiple network including unidirectional circuit means connected 'to said circuit including the other of sai-d windings for reducing the current ilowing therein during the application of one of said potentials with respect to the current flowing therein during the application of the other potential to prevent said relay from operating during said applications of potentials.

5. The combination in accordance with claim 4 in which said multiple network comprises a unidirectional cell for passing currents in one direction therethrough and opposing currents in the other direction, and an impe-dance branch for ley-passingv the said opposed currents about said cell and limiting them.

6. A polar signaling relay, a lineV circuit including a winding of said relay, a balancing circuit including another winding oi said relay, said circuits being connected at a common apex point, signaling means for alternately applying opposite voltage polarities to said apex point and for thereby producing an alternating current in one of said windings, a multiple network including a unidirectional cell and an impedance branch and connected to limit the current flow in one direction during one half cycle through the other of said windings with respect to the current flow in the opposite direction during the other half cycle therethrough so that the resultant flux produced by said windings will be continuous in one direction during the operation of said signaling means.

7. A polar signaling relay, a line circuit including a line winding of sai-d relay, a balancing circuit including another winding of said relay, said circuits being connected to a common apex point, signaling means for alternately applying opposite 2 in which said unidirectional circuit means comprises an impedance serially connected to one of said windings and an asymmetric cell con- Y nected in multiple relation to said one winding.

9. The combination in accordance with claim 6 in which said impedance branch is serially included in said line circuit for control of the normal line current strength and said unidirectional cell is connected in a by-path about the relay winding included in said line circuit to provide a low impedance path for surge currents i in said signaling circuit of direction opposite that of the normal line current.

10. The combination in accor-dance with claim 4 in which said multiple network is connected in said balancing circuit and comprises a current limiting branch for balancing the currents through said windings when one of said signaling Vpotentials is applied simultaneously to both of said windings and further comprising a rectifying device connected in parallel to sai-d branch for admitting additional current through said other winding when the other potential is applied.

l1. The combination in accordance with claim 6 in which said multiple network is connected in said balancing circuit and further includes transient charge absorbing means serially connected to sai-d unidirectional cell and effective substantially coincidentally with transient discharges in said line circuit so that the said resultant ux will be continuously unidrected and of substantially constant strength during the operation of said signaling means. Y

l2. A polarized signaling relay, a line circuit including a winding of said relay, a balancing circuit including another winding of sai-d relay, said circuits being connected to a common apex point, signaling means for alternately applying diierent voltage polarities to said apex point, a condenser and a rectifying device connected in a series circuit included in said balancing circuit, a discharge impedance connected across said condenser and a balancing impedance connected in Vmultiple relation to said rectifying device.

13. A polar signalingY relay, a high capacity signaling circuit including a winding of said relay,V

signaling means for alternately charging and discharging said circuit, a unilateral device in series connection with sai-d winding to at least partly prevent the discharge of said signaling circuit from passing through said winding, a second unilateral device in multiple connection with said winding to at least partly by-pass said discharge.

14. A polarized signaling relay, a line signaling circuit including a line circuit, balancing circuit means, and windings of said relay, a multiple network included in said balancing circuit and comprising an impedance branch for control of normal current in said balancing circuit and an asymmetric impedance branch including a unidirectional .device and transient charge absorbing means in series relation.

15. A polarized signaling relay, a signaling circuit including transmitting means, a line circuit, a balancing circuit and windings of said relay, a multiple network included in said balancing circuit and comprising a current limiting impedance branch, and an asymmetric impedance branch including a unidirectional .device and transient charge absorbing means in series relation for apportioning the normal and transient currents in said windings to prevent kick-off of said relay.

16. A telegraph system including a polarized signaling relay having opposing windings for producing a resultant operating ux, a line circuit including said windings, balancing circuit means included in said line circuit, and signaling means for charging said line circuit and produce a resultant flux in said relay in one direction and for alternately discharging said line circuit, an asymmetric network including a unilateral device connected with said line circuit for preventing the said discharging of the line circuit from reversing said resultant ux.

17. The combination in accordance with claim l in which said impedance means is serially included in said signaling circuit.

18. In a telegraph signal repeating system, a relay Winding for passing impulses between a transmitting circuit and a capacitance circuit, and a multiple branch circuit including an asymmetric branch and connected to said winding to permit normal impulse currents to pass through said winding and to reduce transient currents through said winding due to the capacitance of said capacitance circuit.

19. In a telegraph signal repeating system, a relay having an operating winding for passing impulses between a transmitting circuit and a signal line circuit including substantial capacitance, and having a balancing winding for passing impulses from said transmitting circuit to a balancing line circuit including substantial capactance, and a multiple branch circuit including an asymmetric branch and connected to one of said windings to permit normal impulse currents to pass through said one winding and to reduce transient currents through said one winding due to the capacitance of the associated line circuit.

20. In a signal repeating system, a relay winding connected between a transmitting circuit and a capacitance circuit, and a multiple branch circuit having an impedance branch and an asymmetric branch and connected to said winding to permit the ow through said winding in one direction and to substantially reduce the flow through said winding in the other direction of transient currents between said transmitting circuit and said capacitance circuit.

21. In a telegraph signal repeating system, a relay having an operating winding for passing impulses between a transmitting circuit and a signal line circuit including substantial capacitance, and having a balancing winding for passing impulses from said transmitting circuit to a balancing line circuit including substantial capacitance, and a multiple branch circuit including an impedance branch and an asymmetric branch to provide a low and a. relatively high impedance to transient currents in either direction through said multiple circuit, one of said windings being connected to pass transient currents in both directions from its associated line circuit, and said multiple branch circuit being connected to the other winding to proportion the transient currents due to said capacitances through said windings in each direction for preventing said relay from responding to operations of said transmitting circuit.

WALTER W. CRAMER. GEORGE C. CUNDVIINGS.

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