US2723313A - Pulse correction circuit - Google Patents

Description

Nov. 8, 1955 c. R. FISHER, JR

PULSE CORRECTION CIRCUIT Filed Aprl 15, 195s 2 Sheets-Sheet l Qu En XQSM,

A TTORNE Y NOV' 8 1955 c. R. FISHER, JR'

PULSE CORRECTION CIRCUIT 2 Sheets-Sheet 2 Filed April 15, 1953 ATTOR/VFV United States Patent O PULSE CORRECTION CIRCUIT Charles R. Fisher, Jr., Rochester, N. Y., assignor, by mesne assignments, to General Dynamics Corporation, l a corporation of'Delaware Application April 15, 1953, Serial No. 349,080

7 Claims. (Cl. 179-18) This invention relates to signaling systems and particularly to pulse correction means for step by step machine switching telecommunication systems.

The object of the invention is economy and reliability of operation where diiiicult operating conditions jeopardize satisfactory functioning of switching apparatus.

It is known that in party line working, particularly where a line extends into a rural area and is heavily loaded, the pulses transmitted for controlling switching apparatus are subject to distortion and particularly to attenuation. The rate of pulsing may easily be maintained at any given standard, but the timing of the individual pulses depends on line conditions to the extent that pulses may be attenuated beyond a safe minimum and therefore lead to erratic operation of selector and connector switches. A satisfactory and economical method of insurance is what is known as a lock pulse circuit, that is, the use of a fast operating relay to respond to a pulse which thereupon locks in its op'erated position and remainsy locked under control of the stepping magnet to be operated by the pulse.

The present invention resides in a circuit arrangement for providing lock pulse operation in a selector switch and lock pulse repeating to succeeding switches constituting a pulse correcting circuit. A locking relay is provided in a selector switch and made responsive to all pulses transmitted to this switch, both those employed for setting the switch and those employed later for setting succeeding switches. The locking relay then causes the operation of a stepping magnet in the switch or another relay having the operating characteristics of a stepping magnet and the locking circuit is maintained until either the stepping magnet or the relay of like characteristics has become fully operated. Thus proper stepping of the selector or a succeeding switch may be insured if the pulse is long enough to operate the said fast operating relay even though it may be attenuated beyond the possibility of operating a stepping magnet.

A feature of the invention is a pulse correction means comprising a locking relay responsive to pulses and an unlocking means therefor having comparatively slow operating characteristics. The said locking relay is common to and operates in combination with a plurality of said unlocking means.

'Another feature of the invention is a lock pulse ar rangement for use in a selector switch comprising a common locking relay operating in combination with a local unlocking means in the form of a stepping magnet for local operations and with an unlocking relay for repeating pulses for distant operations, the said unlocking relay having operating characteristics equal to those of a stepping magnet.

Another feature of the invention is an economical circuit arrangement comprising a lock pulse relay employed i in' a mutually controlled circuit and at succeeding stages with the various stepping magnets of a switch and a pulse correction relay having operating characteristics equal to thoseof a stepping magnet.

Other features will appear hereinafter.

The drawings consist of two sheets having three iigures, as follows:

Fig. ll is a block diagram showing how Figures 2 and 3 may be placed to form a complete circuit diagram of a system including the selector switch of the present invention;

Fig. 2 is a schematic circuit diagram including a representation of a calling line, a line circuit therefor, an allotter, a line finder and a portion of the circuit diagram of the selector; and t Fig. 3 is the remainder' of the circuit diagram of the selector.

The two sheets of drawings containing Figures 2 and 3, when placed as shown in Figure l, provide a complete y circuit diagram of the selector switch together with indications of a calling party line, line ycircuit therefor, an allotter and a line iinder to extend the line to the selector. The selector is in its mechanical construction a conventional stepbystep selector, that is, it is equipped with four brushes, the tip brush 300, the ring brush 301, the sleeve brush 302 and the help' sleeve brush 303. it is yalso lequipped with an XX brush 304 and an X brush 305. When the selector is moved by the primary magnet 306 both the regular brushes T, R, S and HS and the control brushes XX and X move forwardly. When a given level has thus been selected, the secondary magnet 307 is operated and this moves only the regular brushes T, R, S and HS, the X and XX brushes remaining at the point where they were moved in the primary movement of the switch.

ln the present circuit arrangement the X and XX brushes control various combinations for digit adding and digit cancellation, an arrangement of great Value in small community dial oices Where certain digits dialed may not bc actually used but are useful formaintaining a uniform numbering scheme. .Details of these connections will be given hereinafter.

Let it`be assumedv that a substation 200 on the line 201i makes a call. The line circuit 202 will be operated in conventional manner and through the allotter 203 a given line finder 204 will be caused to pick up the calling line and extend the connection into the selector circuit shown partly in Figures 2 and 3. When the call is made, the allotter will ground the starting wire causing the vstart relay 20S to operate and this will immediately place a bridge including the resistance 206 across the tip andring conductors leading to the selector. This bridge will cause the operation of the CB calling bridge relay 207 in the selector over a path from ground, the source of dial tone 306, the springs 7 and 6 of the off normal wire.

switch shown in rectangle 307, armature 1 and back contact of the SH relay 208, armature 1 and back contact of the DA relay 308, armature 1 and back contact of the DC relay 309, armature 2 and back contact of the SW relay 310, springs 6 and 7 of the overow contacts shown in rectangle 311, upper winding of the CB relay 207, the tip of the line, normal contacts of armature l of the SR relay 209, front contact and armature 2 of the ST relay 205, resistance 206, normal contacts of armature 1 of the SW relay 210, normal contacts of armature 2 of the SR relay 209 and thence through the lower winding of the CB relay 207 to battery. The CB relay operates and extends a connection from ground, armature l and its normal back contact of the PT relay 211, armature l and front Contact of the CB relay 207, winding of the RD slow releasing relay 312 to battery. The RD relay, in operating,- extends a ground from its front contact and armature 4 to the back sleeve Wire 313 which is extended to the SW relay 210 and thence through armature 1 and front contact of the ST relay 205 to the starter In conventionalmanner (not shown) the original ground .0.11. the, Starter wir@ fram .the alle tterltlsvnw. removed and the SW relay becomes operated in series with the ST relay 205, whereupon the T, R, S and HS conductors will cuitn through thelinender` to` the selector.

Atpthesarne time., the RD relayV 3:12j extends. ground from its armature 2 and front contact to the ,lowerbiasing` winding of the SRA relay 209.` and;;through springs 1 and 2 ofthe of@ normal; set shown, inrectangleV 312, through the` upper winding'of theXD relay` 31Std battery. The SR relay does not become operated at this time but the XD relay operates. Thezciruitlofgthe Selector is'now in a stable condition.and,will-remain so. until thecalling subscriber dials. I

By way of example, it will be assumed thatihecalling subscriber dials ,to a level `in which, the; XXswi-tch comes to rest on a terminal connected to the M wiring. In this case the CB relay 207fl1ows,thezpu-lseszfromthesubscribers dial and upon each such pulse places ground on its armature 1, on .itsback Contact thence through the.

armature v1 and frontcontactrofrtheRD2relay 312, armature 3 and front contactl oli-fthe; SH; relay 208. (operated from armature 3 and4 front'contactofpthe XD relay315),

the interrupter springsofthesecondary'magnet shownin;

rectangle 316, the overllow;V contacts shovvnv in rectangle 3 17, the windingI oi the` H A relay/.318, through its armarV ture 3 and. back contact, through theinterrupter contactsl of the Z magnet shown inrectangle319. to battery. The HA relay, which for the purposes of thepresentinventionwe may describe asta coniparatively,y fast acting. rel'ay, now extends a circuit from ground, itsarmaturef4 and front contact, the armaturel and,back` contacter the SW relayv 310,` the alternate contacts of. armature 7 of the XD relay 315,- the windingofthe primary magnet 306 to battery. The primary magnet operates in this circuit to follow the pulses from the CBzrelay 207. It should be noted, however, that if the:pulseisforeshortened so that the HA relay might become deenergized.- before the primary magnet 306 .could complete .its operation, means is provided to prevent such anoperation. Upon theoperation of the HArelay 318 a locking V.circuit'is established from ground, back contact and armature4 1 of' the PCV relay 320, front contact and armature -2 of the HA relay 318, the interrupter springsof the primary magnet, shownln rectangle 321and thence.. to thecircuit for the energizing of the HArelay sovthat thisrelay, immediately itf operates, becomes locked .and '.will; remain tion until the primary magnet 306.has `completely operated. At this time theinterrupter springsof the primary4 magnet, shown in rectangle 321, willlopenthe .lockingfcir cuit of; the H A relay so that if. by vthis time the pulse-has.

terminatd, ,the HAsrelay will release and by so -doing will? also release the lprimary magnet306'.l

Upon the ,operation of the .HArelay 318, a circuit is' also established from ground, `armature 4- andi front? contact thereof, armaturet and front contact of the/XDv relay. 315\.and thence through thelower Winding thereof to battery. As-theswitch.takes. its rst step in the primary dlrection, theprimary ,otfinormal contacts are-operatd, ar 1d hOS; contacts; shown in rectangleVV 314' open the circuit for the-upper Winding. of the.; XD'relay 315 so that this relay now depends ,onlits locking circuitthrough its lowerA winding.

Thus the =primary magnet 306 .Willrespondtothe'separate pulses, whereas the XD` relay.315 will `respond'to the train-of pulsesas a whole. At the endlof this series of i pulses, the XD relay 315 will release. Thereupona circuit will bel established from ground, front contact' andl armatnre4 of theRD relay 312, back contactand armature 9 of the; SW relay 310, armature-5v' and back contact of the XD relay 315, the XX'brush 304 now assumed to bel resting on a ,contact to which-the'conductor322 is connected so thatthis-.ground connection will beextended through springs 7 and 6 of-thescscondaryI offnormal switchshown in rectangle .323, throughgthe-normal con-.- tasts., o f. armatureefthef SW relai/.13.1.0 landithence over' in thisV condi-` 4., tllsirilit.hsrsinbeferatraed.for the. enersizatoaqf 11.19., HA relay 318. The HA relay becomes operated and extends a ground from its armature 4 and front contact over armature 10 and back contact of the SW relay 310, the normal back contact of armature 7 of the XD relay 315, through the winding ot`,theV secondary magnet 307 to battery. The secondary magnet operates and moves the brushes of the selector afirstistep in..theseondary direction.

Upon the; operation of the secondary'magnetthe circuit for the HA relay31'8 isbroken` bylthesecondary,interrupter contacts shown in the rectangle 316. The HA relay releasesin turnrreleasing thel secondary magnet 317. The S brush 302v howevenhas movedio` its first contact and if the line connected thereto isbusy a ground now on the S brush 302 will be extended over the back contact and armature 2 of the PC relay 320, the armature 5 andback contact ofthe SW relay 31010 the:v circuit;.f,or the HA relay 318,. The HArelay318, andthegY magnet 307 will interact in theirfmutually controlled, circuit-.andy the` brushesof the selector will be driven,i forward automatieally until an idle line is found.. A-t `this time ageincuit will be. extended from aground, the front contactand armature 4.f.of -.the-R-D relay 31.2,4 the winding-oftgthe SW relayv310s`prings5 `and 6 of thel secondary off normal set 323i andthence to the winding of the HA relay 318. The winding-of theSWv relay. 310v is comparatively high, whereas the windingof theHA relay 318 is comparatively low ir 1resistance.soA that theSW relay becomes operated in thisy circuit and thevHArelay remains.unoperated.v Upon the operation of theSWrelay the .circuit of the vHA relay is -opened andy the SW relay VV310 remains operated in a circuit including the. alternatecontactsfof its armature 6 they resistance` 324 to battery.v

In. thsmanner the calling line is extended through;l the armatures l-and-ia-ofv the SW'relay to the tip and yring, brushes 300fand 301V4 respectively tothe succeedingcircuit which may be another selector` or it may be a conneetor,

Thefcallingsubscriber no w dials, another digit. The. CB-'relay 207 responds. to; the pulses. of` this digitin themannerdescribed land Vcausesthepoperation of they relay 318.. Since theSW relay 310 -hasvnowoperatedfacircuit. is established from ground, armature 4| and front contact oftheaHArelay 318, armature 10 and front contact ofY the SWv relay 310. to-thel windinggof` the PC, relay 320 land thenceto, battery. The PQ relay istl one1which has. been adjusted-toI have the same operating, characteristics `as the. primary Vmagnet306 orvthey secondary magnet 307. In-` other words, it is comparatively slow to operate.softhatitzwillf-not open the, locking circuit .off the-,HAQrelaylS at ,its armaturev 1 and bachcontactuntil, a stepping magnet; in a succeeding circuitfhas haclsuflicient-` rimetto; operate. It;.wil1benoted thatthe: HA relay-318iv has a means at its:..arrlnatur. eV liandbackeontact fonref peating pulses. into: the. succeeding; circuit. These; pulses eachconsist of an openingf the-circuit betweenzthesuc ceeding calling bridge lrelay-and at bridge provided' .during dialing,y by thexarmature and'front .contact-'ofthe SH relay, 208. and' during other vperiodsbyltheupper winding of the SR relay 209.

Thus the'HA relay 318 v.is common. to the comparatively slow. operating stepping. magnet 306,- thecomparativelyslowA operatingstepping'magnete307I and the'comparativelyf4 slow ,operating relay 320; f

When ther called subscriber; answersA andV reverses; the; line vin the conventional. manner, the a current` llowtl in; thee upper. windingaof the= SR. `re1ayi209I vwill be reversed. andi. this relay will respond, in turn reversing` the. currentzto: the calling subscriber:forconventional purposes.;

While theY.variousaconnections` whichmay vbe made-rter present invention^,.rthesealternativewirin gs .1 will be'lnriefly.L

disclosed. While it is assumedzthatsithev-trst; two; digitse1 t'o be dialed by the calling subscriber; are those characterizing the particular community dial ofiice in which this calling subscriber is` located, then these twodigits will be cancelled. In' order to do this the N and V wiring will be applied to the terminals of the level dialed by the first digit. When the XX brush 304 vand the X brush 305 come to rest on these terminals, a` circuit will be establishedfrom ground, the V wiring connection-to the corresponding terminal, the -X brush 30,5, the'back contact and armature 4 of the XD relay 315 (when this relay becomes released), the back contact and armature 4 of the DA relay 308, the armature 8 and back contact of the SW relay 310, the armature 2 'and front- .contact of the CB relay 207, the armature 4 and back contact.y

ofthe DC relay 309, thence through the winding of this relay to battery. The .DC relay operates in this circuit and locks through the alternate 'contacts of its armature 4, thence in parallel through the back contact and armature 3 of the DA relay 308 and thebackl contact and armature 1 of the XD relay 315 to armature 4 and front contact of the RD relay 312.

At the same time ground on armature 4 'of the.RD

relay will vbe extended through the back contact and armature 9 of the SW relay 310, armature 5 and back contact of the XD relay 315, the XX brush 304 to the terminal on which this brush now rests and which is connected 4to the N wire 325 through the front contact and armature 5 of the DC relay 309, now closed, the front contact and armature 5 of the RD relay 312 and thence. through the springs 4 and 3 of the X off normal set shown in rectangle 326, the winding of the Z release magnet 327 to battery. Thus the switch is released and will return to its normal seized condition with the CB relay 207, the RD relay 312 and the XD relay 315 operated. The DC relay 309 will also remain operated.

AThe calling'subscriber now dials the second digit of Vthis number which designates his own oice and in this case will reach a level characterized by the Z wiring. As the XD relay releases, a ground on armature 4 -of the RD relay 312 will be extended through the back contact and armature 9 of the SW 'relay 310, the armature 5 and back contact of the XD relay 315, the XX brush 304 to a` contact to which the `Z wire 328 is connected so that this ground will now be extendedthrough the front contact and armature 3 of the DC relay 309, the winding of the DA relay 308, the normal back contact of armature 2 thereof to the battery supplied through the Z interruptor springs shown in rectangle .319. The DA relay 308, in operating, locks in. a .circuit from battery to alternate contacts of its armature 2, its winding, its front contact and armature 3 to the ground on armature 4 ofthev RD relay 312. As the DA relay operates it will extend this locking ground through armature 3 and front contact of the DC relay'309, front contact and armature 5 of the DA relay 308, front contact and armature 5 of the DC relay 309 to the circuit for the release magnet 327 in the manner hereinbefore described.

As the switch releases the selector will again come into the condition awaitinganother series of pulses. Asthe XD relay 315 operates, the locking circuit of the DC relay 309 is opened at the back contact and armature 1 of the XD relay 315 so that the DC relay releases. Now the calling subscriber may dial any given number whereupon with the DA relay 308 operated the switch will successfully make connection to an idle line in the wanted level. The idle line hunting operation will be started from ground, front contact and armature 4 of the RD relay 312, armature 3 and front Contact of the DA relay 308, armature 3 and back contact of the DC relay 309, armature 2 and back contact of the XD relay 315, springs 7 and 6 of the oft normal set shown in rectangle 323 and thence through the circuit hereinbefore described for the operation of the HA relay 318.

Various combinations to fit varying operating situations may be provided by the use of the Q, M, Z, N and if this level is dialed beforethe first added digit.

. of the V` wirings indicated in the lower righthand corner of Figure 3. Thus the N and V wiring on the first levelto be dialed by a calling subscriber will cancel that digit, but allow the level to be used after a second added digit has been similarly cancelled.y The Q and V wiring may be used on a level to beused before but not after thev second added digit. The N wiring only is usedon a level requiring busy tone if dialed before the rst added digit, will be employed for digit cancellation after the first added digitand `will allow the use of the level after the second added digit. The Q wiring will be used on a level requiring busy tone if such level is dialed before the first added digit and will allow. the use of the level after the first added digit. The Z wiring is used only on levels reached by a second added digit and provide busy rtIcilie 1s wiring also provides for use of the level after the second added digit. The Z and V wiring is used on first or second digit adding levels with the use of all levels after being dialed the first time. The M- wiring is used on a level to be used the first time dialed. If there is no wiring on a level then busy tone will be applied to the calling line if such level is dialed before the first added digit and the use of the level will be allowed after the second added digit.

` XX brush 304 on a terminal having no one of the Q, M,v

Z or N wiring connections and the X brush 305 on a terminal not having a V wiring connection, then there willbe noway of starting the secondary or'idle line hunting movement of the switch and the switch will remain as set in its primary movement. Thereupon the source of busy tone 321 will be connected through springs 5 and 6 XON off vnormal set shown in i rectangle 307 and thence over the circuit previously traced through the upper winding of the CB relay 207.

if the first digit is to be immediately effective, then the DA relay 30S is operated to open the dial tone and busytone circuit as by the use of the M wiring.

if but a single digit is to be added, that is dialed and then cancelled so that the second digit will successfully set the switch, then the Z and V Wiring connections are used. The V wiring will cause the operation of the DC relay 309, the wiring will thereupon cause the operation of the DA relay 308 and thereafter the release of the switch. Upon the first pulse of the next digit the DC relay 309 will be released and this second digit will become effective. l f

If two digits are to be cancelled then the N and V wiring will beused so that on the first digit the DC` relay 309 will be operated. relay 308 is operated, as by the Z wiring'this digit will be cancelledand the DC relay is released,ileaving only the DA relay 308 voperated so that the third digit will be effective. t

Thus a flexible arrangement is provided so that the selector may be adapted to various operating conditions.

What is claimed is:

l. In a telecommunication system, 'subscriber lines each having dial stations thereon, a selector switch for extending connections from said lines under control by said dial stations, said selector switch having a comparatively fast operating relay responsive to dial pulses transmitted from said dial stations, a locking circuit for said relay, a stepping magnet for said selector switch controlled by said relay, means controlled by said magnet for opening said locking circuit, means for repeating pulses transmitted to said fast operating relay, another relay having comparatively slow operating characteristics, said characteristics being like the operating characteristics of said stepping magnet, said other relay being under control of said fast operating relay and means controlled by said other relay for opening said locking circuit.

2. In a telecommunication system, subscriber lines each having dial stations thereon, a selector switch for If, on the second digit, the DA- extending connections-from said-'lines under control by L tliiilfstations, said" selector switch having a comparatively fas'tf operating relay, a locking circuit forA said relayjaplu-ral-ity of stepping magnets and relays all having- -like operating characteristics, each of said magnetspand` Vrelayshaving meansY for opening said locking circuitQ-sjaidcomparatively fast operating relay having controlover each of saidmagnets and relays, means for switchingsaid control of said comparatively fast operating locking-relay vto each of saidmagnets and relays in turn, andfpulsefrepeating contacts controlled by said fastoperat-ing relay,

""3, In a telecommunication system havingI dial station lines, selectors having'switch' stepping magnets respon-Y siyglthe'rto andsucceedingA circuits and switches accessible to said selector-s,-means in saidvselectors for lengthening attenuated pulses `transmitted from said dial stationlines-to said selectors and for repeating said lengthened pulses into said succeeding circuits consisting of a circiiit varrangement includinga stepping magnet responsive yto4 pulses from a said dial station line having mea-ns to eontrol-thelength of pulses transmitted thereto, a relay' ofcharacteristics like `to those ofsaid stepping magnet ylikewise responsive to pulses from a said dial station line and having means to control the length of pulsestransmitted thereto and means responsive to an operation `of' said selector by said stepping magnet in entendinga said dial station line to a said succeeding cir cuitand switch for transferring a connection between a saidfdialstation line and said stepping magnet to a connection between a. said dialV station line and' said relay having characteristics like to those of said stepping magnet.

4. In a .telecommunication system having dial station lines, yselectors having switch stepping magnets, succeeding circuits and. switches accessible to said selectors, a calling bridge relay in eachsaid selector, a stepping magnetyin eachsaid selector, said calling'bridge relay and said stepping magnet being connected in a mutually controlling. circuit, a repeating relay in each said selector -fnr repeating-pulses from a said dial station line to as-aidsucceeding circuit and switch, said repeating relay having` characteristics like to those of said stepping 'magnetandmeans responsive to the operation of said selector in extending asa-id dial station line to a selected succeeding `circuit andgswitch for substituting said repeating relay forl said steppingv magnet in said mutually controlling circuit.

5. In a telecommunication system, subscriber llines each having dial stations thereon, a selector switch for extending connections from said lines under control by said dialtstatiohs, said-selector switch having a control circuit including-,fa comparativelyV fast operating relay responsive-(nto ydial pulses transmitted from said d ial s tationsQa locking circuit forl said relay, a stepping magnet for said selector switch controlled by said fast operating relay, means` controlled by said stepping magnet for opening said lock-ing circuit, means for repeating pulses transmitted to said fast operating relay, another relay havingcomparativelyslow operating characteristics, said characteristics 4.being like thel operating characteristics of sail,..stepping` magnet, said slow relay being. controlled by .said Afast.nperaing..relay, meansf controlled` byisaidslWrela-y for opening s-aidlocking circuit and-means 'for switching-from..control over said stepping. magnet bys'aidifast operating relay to. control over-'said` slowre'lay by saidfast operating relay.

6. In a telecommunicationsystem, subscriber lines .each4 having dial=stations"-thereon, a selector switch for extendj' ing connections Yfrom nsaid linesunder control` by said dial stations,v succeeding circuits accessible `to said selecV tor. switch, said selectorswitch having. a controlfcircuit includinga comparatively fast operati-ng relay,'a locking circuit ,for said relay, ystepping magnets for- -saidselector switch for. moving saidi switch infprimaryv and secondary directions'said stepping magnets .being under control by said; v'fast operatingrelay,-ndffech saidy magnet havin-g means for "opening said lacking circuit, a cut throughrelay for changing the circuits of saidfselector switch afterr said stepping magnets,r have. driven' said selector switch into connection". with a succeeding .extended connection, a relay havingl,oper-atingcharacteristics like theoperating characteristics ofisaid-stepping` magnets, means controllediby vsaid cut. through relay lto transfer- Acontrol over said. stepping.. magnets by said fast operating relay to.-controloverlsaid lastrrelay' bysaid fast operating relay, said.z.last.relay having. lmeans for opening `said`locking circuit :and-means controlledby said fast 'operating'relay for repeatingndial pulses intoaselecte'd succeeding circuit. 7. a telecommunication system, subscriber lines each hayingidial stations thereon, a selector switch for extendin'giconnections from said. lines under control by said dialV stations, succeeding` circuits accessible to said selector switch, said. sel'ectorl switchA having a control circuit-Ain- Cluding ,a comparatively fast operating relay, al locking circuit for said relay, a primary steppingl magnet for said'- Selectorswitchk .controlledfby said'fast operating relay and responsive-.,-to. dial pulses' from one of jsaid stations and havingmeans for openinglsaid .locking circuit,- a secondary stepping magnet for said selector switch controlled by .said 'fast operatingirelay and having means for opening said, locking...circui t for. automaticallyv moving s'aid4 switch.. in anidle succeeding cir-cuit hunting operation, a Qutthrough. relay responsive to the selection ofvv an idle succeeding fcircuina pulsecorrection relay having like operatingcharacteristics .toLsa-i'd stepping magnets, saidpulse correction. relay` being controlled by saidfa-st op; erating relay` and 'b eing responsive to dial pulses from Qneof said. stationsand .hai/ling. `means for opening said lQQkingcircuit, said cut rthroughl relay having means for v 'transferring ,t-he.,co ntrolb.y said fast operating relay over said stepping magnets to control by said-tast operating relay ,oye-ri saidv puiser, correction relay andmeans 'coni trollen` by said, fast operati-ng. relay for 4repeating dial Ettlsesmto a said selected succeedinglcircuit. 'i

vlfrrcasss @Ctitanic-therme cf.: fthispatentY UNIrED srAfrnsrArsNrs

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