US2328241A - Coded track circuit signaling system - Google Patents

Description

S. N. WIGHT CODED TRACK CIRCUIT SIGNALING SYSTEM Filed July 26, 1941 Aug. 3l, 1943.

ing current.

Patented Aug. 31, 11943 SYS Sedgwick fWight,` Rochester,A N. Y., assignor to l General Railway Sig-nalxCompany,` Rochester,

Application July 26, 1941, serial No. 404,212 j 19 claims. (c1. 24o-3s) t u This invention relates to single track railway signaling lsystems and more particularly to a coded `track circuit of the duplex type `for such system.`

v By a duplex coded track` circuit is meant a A `track circuit in which there Iis a track relay at `each endthereof which responds to a code applied to the other end thereof and wherein codes vmay be applied at either or both ends simulta- `neously and received at the opposite `end that at which they are applied. a

4In accordance with the present invention it is from `proposed to apply pulsating alternating current `across theA rails at opposite ends of the same track circuit in such atmannerv that a wave of one polarity is appliedduringthe first half of a cycle of alternating `current at one end of the `track circuit and so that a `pulsating current of the opposite polarity waves is applied during the secondhalf ofeach cycle of an alternating current. Ian other words, pulses of direct currentlarealternately applied to oppositeends of `the`t`ra`ck circuit at a rate corresponding to the i Ireqency of the alternating current employed, and in such amanner that one of the rails of the railway track alternately become plus v(1+) and minus once for each cycle of alternat- That is, current of the saine polarity is alternately applied to one and then the other of the track rails. In this proposed cron- "structio'n these `pulses `of directcurrent are den rived from a rectifier of thestatlc type as disi tinguished from a rectiflerof either the vibrating reed or the commutatlngtype. In the prior j application of HoppeSer. No. 253,837 pulsating `currents are similarly applied to opposite'ends ola track circuit bya vibrating reed actuated from the same source of alternating current. If a vibrating reed is used for obtaining pulsating` `direct current from analternating current systemfsuch, for instance, as 'is `disclosed in the Hoppe applicationabovereferredv to, there is little danger ofnobtalning a false clear indication,`

this byreason` of the fact that a vibrating reed rectier does not readily become short circuited.

II, however, "arectiiler of the static electro-lytic orco'pper-"oxide type is employed, as is proposed inthe system of the present invention, a false clear indication could very easily be givenby such rectier becoming short circuited, as is very commonly the case with static rectiiiersof thistype, wereit not for the provisionlof suitable checking means. i f

proposed to employ a rectiiier or` the static cop- In `accordance `with the present invention it is i `per-einde type for applying `such pulsating current tothe track circuit and also for detecting thev polarity of the pulsating current received at r the track relay end of such` track circuit, it being further proposed to employ a track relay of the polar `type connected in series witharectiiier of ,the` single wave type to detectpulsating current 'oia particular polarity. `It is` also proposed to employ suitable checkingmeans for causing` an l0V oneofthesei 4static"rectiiiers breaksjfdown; a a

Other objects, purposes y,andcharacteristic feaassociated'signal to indicate stopfwhenfeither tures `of the present invention will in part be pointed out in the specificationhereinafterQ and will in part be obvious from the accompanying drawing which;

Fig. 1" shows the invention Vapplied to one `section of railwayftrackf at theentrance` to `each end ofwhich there islocated a sigrlaljforgov` erning the entrance Vfof traffic into such sections andi y l: i i ii Fig. 2 shows a modified form'of the invention -rails 1010i a railway track lhave been-shown dl- -vided into blocks` or sections by insulating joints I;2of which the block `N and theadjacent ends Ofitheiblocks, M and O onlyhave ,beenlillustrated @At the `left end of the blockN is shown a signal i S2 which governs `the movement offeast-bound tralllcy into the 'block N and atthe `east endof this 'block lN` is shown a signal .Si which governs west-bound tramcninto thisbIock. :These Asig-q nalsSZ and` SI `are controlledrespectively` by crcludes 'the `usual de-coding apparatus and directional` stick relay controlcircuitsa'nd apparatus .well Aknownin the artsuchf, for instance, as are illustrated in thepriorapplication of Hoppe above i referred to. rIi'he fcode a a a following track relayior 'governing *east-bound? traffic `has 'been designated CFTE andis connected-*inseries with a rectifier:

andacrosrsthetrack rails lll at'the west @ndr @tithe block Nain jwhich reference characters the' letter E denotes apparatus for governing east-bound trafllc` Thiscode following track relay CFTE receives its'energy from the `secondary winding of a transformer I'E having a rectier RIE included in Vseries therewith and lo- 2; cated at the east end of the block N. The secondarywinding of the transformer TE is also provided with the usual series impedance IE.

Identical apparatus is employed for governing west-bound traffic of which each element has been designated by the same reference character' except that the letter W has been substituted for the letter EK VAlso the pulsatingr current supplied by Vthe transformer-rectiier TUV-RW has been illustrated by solid arrows, whereas the pulsating current supplied by the transformer rectier 'TE-RE has been illustrated by dotted arrows. f

It is readily seen that failure of the rectier PtE, for instance, by becoming short circuited, f..

would allow the code following track" relay CFTE n' to become energized by current of either polarity.

For this reason, the'checl: relay CKIE has been` connected in multiple with the rectifier This provision is resorted to in order to further f assure against falsev .0l-'aeration of the track relay CFTE. f'Ihis track relayfhas also been made polar, it being. provided rwith a polar contact 15E Awhich maybe' operated frornits biased position, to which it isbiased by alspring ISE, only if the currentap'pliedthereto is of the proper'polarity,

suchk as i's'perrnitted to'iowthrough the rectiiier BSE; lItis readily. vseen that if the rectier RIW 'connected in series .with trie ksecondary winding of the transformer TW should breaky down ory become short', circuited -it could directly apply Current@a'tileast iIiterniittently,v tothe code following -track rielayf'lnTlil through the medium .of the rectier R3E, because such break downl of @rectifier RIXV would allow both waves` of each 'cycle of 'alternating lcurrent to flow.A For this reason, asecond check relay CK2W has beenconnectedto. receive energy from the secondary windings of the transformer TW, whichenergyis pulsating current derived by rectification of this alternating current by the'rectier RIW.l This shed; relay CKzWfzisof Suohconstruction that it will pick up its armaturev and close-its front contacts if pulsating current is applied thereto ,but whichgwilldrop to its deenergized retracted I position'fi thereafter Y.alternating current y'applied theretd-assurning ofcourse that these currents are .derived from the'same source 'of alterhating current potential, ethe *pulsatingy Ycurrent 'thereof being v`rectified bythe rectifier R'IW.- It

is,:t herefore, readily seen thatthe breakingv down or [short circuiting of. the rectierA RLW` will .be

tional explanation as to the operating characteristics of the relays involved. The track relays CFTE and CFTW are polar devices so that they will not respond to the polarity of currents passed by the rectiers RIW and RIE, respectively, local thereto but will respond to the polarityof current passed by the rectiiiers RiE and RIW, respectively located at :the ends of the block opposite to These 'track relays CFTE and,

such relays. CFIW are very quick acting so that they are A.capable of following the impulses of the fastest pode assumed to be 120 impulses per minute in {the particular system specifically disclosed and at the same time these track relays are not fast enough to follow the pulses of the pulsating currentwhich may be of from 60 to 100 pulses per second. For this'reason these track relays have been called code following track relays. The check relays CKlE and CKIW, on the other hand, are not code following in their speed of operation but instead areeslo-w enough dropping to stayup' between-impulses of the slowest code -assumed'to be a codeof 75 impulses-perminute in the system disclosed. It is thus seen that the check relays CKIE and CKlW- will during l10n-Occupied conditions ofthe block N remain-energized contnuously assuming, of course, that the re'ctiflersRSE and RW are in goodrectifying condition but that thesecheck relays-will assume 'their `deepersized position, during occupancy of theblocknfat some point not too great a distancefromthe end at which such-check relay is :located In other words, the check relays and CKiW may be used to indicateoccupancy for approach indicae tion lpurposes or for piokingfup a directional stick relay. `Forinsta e. aba-ck Contact. of relay CKIE may be used stckrelay for sienaliSZ inthe same way'as back contacts rand 31| in -said vHoppeapplication yare used to sick un adretional stick relay.

It is readilyunderstoodethat the-breaking down, or becoming short` circuited, ofthe rectiiiers -RZE .or BBE-will cause `dropping or the relays CFTE- Qr yCKIE, respectively. The drop awaycharac- 1teristics of these relayszCF'IEand CKIIE is such that the open circuitingeof` the rectifiers R215: or

R3E will cause dropping ofl the relayin series therewith, name1y,.the relay @Kin .er CFTE', respectively. Furthermore, .the vcheck Vrelay CKIE will drop. upon openlcirou'iting,v ofthe recti-` er RIW, whereasfor reasons already explained the check relay-C Klywill .drop upon the rectifier manifested `by 'the dropping. of thecheckirelayA CKZW. ,This circuit, including the` secondary windingjof the transformer TW,'t`he rectifier RIW, andI the -check relay CKZWUand 'the series f impedafrrce IW heretofore mentioned in `connection withiapparatus located at the east endI of the y .block N and there designated IE, checks the rectifying effectiveness; of the rectiflerfRlW.

.Attentiongisv directedto thezfact that/the coding .contact ISE can yonly apply'coded currents'tolthe decoding and directional control apparatusECfif .beni er the; remys cri-mend CK2-ware lenergized, as is evident from the front oontactsfHE .g

and1I8`W,r espectivsely; of these relays included .in series with :the contact-, [5E off the code following track relay Since thek apparatuses at both 'ends-off the'1 block,N are. identical like devices usedfor west-bound trafc have been designated bythe same reference characters as those for east-bound trarne except that suixes have been used instead ofsuiiixes E. i

, At this point it maybeiwellto give seine-addij RIW becoming.' short ci-rcuited.' The rectier R2E has three'f important vfunctions to. perform. One, it servesto allo-W Acurrent for the .check relay CKlEto vflow; two, itprevents the current flowing through relay. CK iE Vf roniflowing'through track relay fand.y three,it .renders track relay CFIE slowgdroppng to anex'tent toffollow the 75 or` 120 impulseperlrninute code.l What has beensaidabout the operating characteristics ofthedevicesatthe westendfofblock N isy also true ofcorresponding devices at the east end of n Dickv up the :directional n number `of contacts required on thecode follow;` ing relay. `In all other respects'the system of Fig; z and functions the same `as thatl 2 is `constructed ofFig. 1.` Y n i v operation Let us firstA assume that eachof the blocks N, t. M` and O is unoccupied. Under this condition of traic, the block N being unoccupied, the coding` relay CRW is` intermittently energized tovcause,v

the` coding contact 20W to close and 4open at a coding rate to create 120 impulses of pulsating current per minute. This pulsating current flowsA from the secondary winding of the, transformer TW,through` the rectifier RIW, to' the lower track rail II) then through this rail of the track,

to the east end of the block N, through the Windings `of the codeu following track relayCFIW,

through the rectifier RIlW,` to `the other" rail of s the block N, back to the` west end of theblock NQ@ and through coding contactZUW and .serles'imf pedance IW, back to the secondary winding of the transformer TW, 'I'he iiow of this current of 120 impulses per minute, of which each impulse constitutes a plurality of direct current pulses,

. causes the code followingtrack relayCFI'W toA assume `its energized position intermittently 120 times per minute. The pulsating current in the circuit'just traced is of sucha polarity as to'in` termittentiy move the Contact ,15W to the rightM against the tension of the spring ISW to actuate t the decoding apparatus constituting part ofthe apparatus conventionally illustrated byfthe rec.

tangle WC. The `potential existing across thel secondary winding of the transformerTW alsof energizes the check relay CKZW by pulsating cur' rent of the same polarity as the pulsating current supplied to the code following track relay CFIW, bothof these currents being supplied through the mediumof the rectii'lerRIW.` As already Pointed` out, the checklrelay CKZW isfso constructed that it will `pick up onpulsating current, butwill not be maintained up onfalternating current derived from the same transformer from'swhich such pulsating" currentv is derived byrectilcation. There is still another circuit whichis supplied fromthe' secondarywiriding ofthe transformer` TW, namely; `the circuit including the rectifier `RIW, the `checkrelay CKIE, the rectifier RZE, the lcoding contact 20W, and the seriesirnpedance` f IW. The current inthe circuit just traced flows through `thecheck relay CKIE and `maintains this check relay energized so long as the rectifier R3E not broken down and the block N is vnot occupied. i If `the rectifier R3E should break down it wouldicreate a shunt around the relay CKIE causing this relay to assume its deenergized posi` i tion. It is again pointed out that this checkrelay CKIE is so slow dropping that it will not drop between the pulses of either the 7 5 impulse code or the 120 impulse code appliedthroughthe coding contact 20W. If neither a code of'175 impulses per minute` or a code of 120 impulses per minute is i applied tothe coding relay CRW, the coding coni tact 20W assumes its denergized position V.con-

tinuously and causes pulsating direct currentto` be `appliedto the track circuit and `to the check relay CKIE continuously. It is thus .i seen that t thettransformer TW suppliespulsating `current i continuously tothe checking relay`CK2W and supplies pulsating current intermittently to the check relay CKIE and the code following track relay `CFIW at the opposite end of the block and in accordance with the code then applied to theY coding relay CRW.` In the same manner as the transformer` TW applies i pulsatingcurrent at winding of the transformerTE applies similar pulsating current coded at either the 75 or `the 120 impulse per'minute code rate to the! east end of the block N, and this coded current may flow through the check relay CKIW and through the code following trackrelay CFTE. Similarly, a pulsating current is applied to the `check relays CKIW and CKZE from the secondary windingV of the transformer TE. f

Under normal clear traiiic conditions, as has justbeen assumed, `both ofthe coding relays VCRW and CRE are energized and deenergized at` the 120 impulse per minute coding rate, as a result of which both of thecode following track relays CEPE and CFW I are energized intermittently 120 times per minute, .which results `inthe code' following contacts ISE and VIEW assuming their right-hand position 120 times per minute. Also,

for reasons just explained the check relays CKIE p and CK2W, aswell as the check relay CKIW, and

the check relay CKZE, assume `their energized i position continuously, whereas thecode following track relays CFTE and CFTW are intermittently` picked up at the` 120 times4 per minute rate. The i contacts I'IE, IBE, I`IW and I 8W are, therefore, continuously closed andthe contacts IEE `and `It'iWare `intermittently. operated `to the righthand actuated positions.` This actuation` of lthese ,contacts I5E and I5W at the 120 times per: minute rate causes th'eidecoding devices consti tuting partgof the apparatuses EC and WC, re-

`S2 and S I, respectively.

spectively, to`close clearing circuits for the signals `Let us now assume that an east-bound train"V signal SI to its caution indication condition.

This circuit constitutes part of the signal con-` trol circuits conventionally illustrated by th t dotted line ISW. s

Let us now assume that the east-bound train in the block M passes the signal S2 landmoves.

into the block N. This results in continuous deenergization of both of the code following track relays 4CF'IE and CF'IW and results in bothof the signals S2 and SI being controlled to display a stop indication, because during such occupancy of the block N no coding current from the transformers TE and TW can reach the track relays CFIE and CFTW, respectivelyy and the code following; contacts ISE and I5W will remain at rest and cause the `ile-coding apparatus EC and WC to manifest danger trafiic conditions.

Let us now assume that the ltrain under consideration has passed entirely through the block N and `through the block O` and that all of the` apparatus returns `to its` normal condition in which both of the signals S2 andSI display` a clear indication. Let us also assume that the rectifier R3E has become short circuited. This will `result in the pulsating current formerly flow` ing from the secondary winding of the transformer TW, the rectifier RIW, the check relay CKIE, the rectifier RZE, and the coding contact 20W to flow through the broken down rectifier R3Elnstead of through the `check relay CKIE.

Inother` words, the check relay CKIE will as.y

- either the 75or2120 impulse per minute coding"` rateto the west end of the block N the secondary sume its deenergized retractedposition and `open the circuit leading to the' decoding apparatus ycontained within the vrectangle EC'and cause l'the operation of the signal S2 yto its danger or stop condition. Similarly, if-'the rectifier RIW should become short circuited, this/would result in alternating current instead of pulsating current being applied tothe check relay CK2W, as a `result of which'this check relay CKZW would assume its deenergized retracted position. If the track 1vrelay CFTE were not constructed polar Iandthis` latter check were not provided the coding contact 20W could, through the medium of the secondary winding of the transformer TW, the `rectie'r RIW, the broken Adown rectifier RSE, supply pulsating current to the code following tra-ckv relay CFTE and hold Ythe signal Si! falsely clear by a locally generated code. This pulsating current is, however, Vof the w'rong polarity and since the code following track relay CFTE is a polarv relay, no false clear indication would'be given under the assumed conditions at a particular end of the block N due to the Vcoding apparatus locatedat the same end. Thev relay CKZW picks up on pulsating current and drops away on altery ously. What has'been said about the apparatus at the west end ofthe block N is likewise true' ci the apparatus at the east end of the block N.

` `'Stating this functioning oiv the apparatus in" somewhat diierent terms the rectifier REW prevents the application of pulsating current of" the wrong polarity to the rails at the west end of the block N so that this pulsating current ciV the wrong polarity cannot operate the code'- fol-'- lowing track relay CFTE at the West end oil the block.Y The check relay CK IEEt has been to check the rectifying eiectiveness of' the' rec-f tii-ier RSE `which is included in series with the'v code following` track relay CFTE. This check" relayCKlE is, therefore, provided to openfrthe circuit controlled-by the contact iE ci the-.code following track relay `CFIE in the event that thisI code following ltrack relay CFTE is energizedby local current which flows through the' rectiiier RSE'. Thel rectierzR'ZE has primarily been ein# ployed to provide a path for the current' which flows through the check relayl CKiEL and seciondarily makes the tra-ck relay CFTEF sniiicibntly slow dropping' so as notte chatter responseA to be understood that the particular embodimentillustrated has been selected to iafci-l'itateidescrip'- tiene-i' the apparatus'embodying the: inventlhn and the disclosure of the functions/it performer, and it is further desired to be -understooir` that' various changes, modifi-cationsand additiorrsniey be madey to the invention withou-t'- departing front the spirit or scope thereof, except as. demanded by the scope of the following claims.

What I claim as new'isl: l i 1. In combination with a:` section off track di'- vided from adjacent sections ley-insulating joints,

a single waverectiner ioreachend of', said sers; tion, a track relay? for .each end of saidlsection each connected in series with the associated singie wave rectifier and connected across the rails of said section at that end, said rectifers being so poled that one rectifier allows current to iow from-onerail and the otherlrectifier allows cur-v rent to'iiow from the other rail, a source of alternating-current available at both ends of said section, another single wave rectifier at each end of said section, a coding contact at each end of said section, a-transformer vat each end of said lsection having its primary winding energized from said source and the secondary windings of which arev connected in series with the associated coding contact and said another rectifier, said transformers being "so connected and said other rectiers being 'so poled in the secondary windings tharcurrent impul'ses'are alternately applied to opposite ends of said section each current iinpulse being of a polarity so that it cannot ilow' through the track relay and its associated rectifier at that end but can flow through the track relay and its associated rectifier at the other end,j

a check relay connected in multiple with each rectifier associated with a track relay, and decoding electro-responsive means controlled by the track relay and check relay at one end-of'said section. f Y

2. In combination with a section of track divided from adjacent sections by insulating joints, a single wave rectier for Aeach end. of said. section, a track relay foreach end of said section and connected in series with the associated single wave rectifier andconnected across the track rails at that end of said section, said rectiers being so poled thatone rectifier allows current to flow from one rail and the other rectifier allows;

currentto flow from the other rail, a source of alternating current available at both ends of said section, another single wave rectiiier at each end ofsaidv section, acoding contact at each endoi said section. a transformer at each end of said. section lhaving its primary Winding energized from said. source the secondary windings ci which are so connected in Series with the associated coding `contact and said yanother rectiner so that. current impulses are alternately applied to opposite endsfof saidsection each current impulse being poled so' that it cannot iiow through thetrack relay and its associated rectifier at that end but can flowthrough the track relay and its as-v sociated rectier v at the other end, checking means for checking the' rectifying eiiectivenessrof one of said'rectifiers, and decoding means at each endr of saidy section controlled by the associated' track relay andi checking means.

3.. Ini combinationwithfa section of track d-ivided from adjacent sections by insulating joints,v asingle wave rectiiier for each end' of said section', 'ai tra-ck relay for each end of said section and-connected in series'with the associated single waveV rectier and connectedfacross the track rails at that end ofk said section, said rectiers being, sof polled in the circuit that one rectiier' allows current toflow fromone rail'and theother rectifier allows currentto iiow" from the other rai-lr,y acsource of alternating current availablea't both: endsof said section, another single wave rectifier ati each end of said sectionraicoding conf-y tact at eachend otsaid section, a transformer ati each; endloff saidsection havingits primary windfing energized from said source and? having its secondary wind-ingsl so'. connected' in series. the associated; coding Contact and' the associated another rectifier so that-current impulses are alternatelyapplied to` opposite ends of said section fof which eachcurrent impulse is poled so that it cannotiiow through the' track relay and its associated rectiiier at that endbut can now through 'thetrack'relay and its associated rectiiier at the other end, relay` means 'for ychecking the rectifying effectiveness' of eachrectifier connected in `series with a secondary winding'of such transformer;` and electro-responsive decoding means 'controlled bysaid track relay and relay means. 4.`I.n`combination`with` a section of track divided from adjacent sections by insulating joints,

connectedcacross thetrack rails and in series with the associatedsingle'wave rectifier" at that c end'of said section, said rectiiiers being so poled `in theirrespective circuits that one rectifier allows current to'flowfrom one rail and the other "rectifier allows current tcl flow from the other railof said section,` a sourceof alternating current'availablejat both ends of said section, an-

other single waverectiiier ateach end of said section,` a coding contact at each Vend of said section,

'a transformerat-e'ach endof said section having "a" single wave rectifier for each endof said sectionjatrack relayat each end of said section its"` primary `winding energized fromV saidsource and having its secondary winding so connected 'inserieswith the associated coding contact and the associated another `rectifier so that current impulses larealternately applied to opposite ends of said section eachfcurrentimpulse being poled orniarywindingv `of such transformer, asignal at each end of said section for" governing the entrance of traffic intothese'ction at'that end,\a`nd aclearing'circuit for each' of said signals `includ- `ing"'front"contacts"ofthe vtrack relay and front -contactsofthe check relays associated with that signal.` "`l i y d c `5.111'combination with a sectionfoftrack divided from adjacent sections by insulating joints,

a" transformer having a primarywinding and a f correspondingly poled secondary winding foreach end of` said fsection, a source of alternatingv current forjenergizingthe primary windings of said -transformers withfcrrespondin'g instantaneous polarities, ajtrackrelay for each/endet said section, two sigl'ef'wave Irectiflers for eachend of `said section,` said track' relays andthe secondary 'windings' of said transformers being correspondingly connected in multiple across theV track rails and each havingone of said half-wave rectiflers included inseries therewith,sa-id rectiflersbeing sopoledin their respective circuits that the half- Wave of current supplied Vto the track rails by the secondary winding 4and the rectifier included in series therewith cannotflow through the associated track relay and the rectifier includedin series therewith but can ow through the track relay and the rectifier-included in series therewithatthe opposite end, whereby impulses of current can flow alternatelyto thetrack relays at opposite ends of said section from such transformers, means for checking the rectifying effectiveness ofisaid recticrs, and signaling means `controlledby said track relays.`

6.` In combination witha` section of track di.l

` videdfrorn adjacent sections byinsulating joints; `a transformer having a primary winding anda secondary winding for each end ofsaid section, a source of alternating current for energizing the primary'windings of' saidtransformers, a` track relay for each end of said section, two single wave rectilers for each end of saidsection, said track relays and the secondary windings of said transformers being so connected in multiplefacro'ss the track rails and each having one of said half-wave rectiers included in series therewith so poled that the half-wave of current supplied to the track rails by the secondary winding and the rectifier included in series therewith cannot flow through the associated track relay and the rectifier included in series therewith but so that iinpulses of currentiiow alternately to the track relays at opposite ends of said section from such transformers, a check relay for checking the rectifying effectiveness of each of the rectiners connected in series with the secondary windings of said transformers,` a check relay for checking the rectifying effectiveness of each of the rectiflers connectedin series with saidctrack relays, anda signal governing the entrance of traiiic into each end of said sections each controlled by the track relay and the two check relays located at that end.

7. In combination with a section of track divided from adjacent sections by insulating joints, a transformerhaving a primary winding and a secondary winding for `each endv of said section,

asource of alternating current lfor' energizing the primary windings of said transformers, a track `relayforeach end of said section`,`two single wave rectiiiers foreach end of said section, saidtrack 'relaysv and thegsecondary windings of said transformersbeingisolconnected in multiple across the track rails and each having one of saidhalf-wave rectiersrincluded in series therewith so poled ir'rtheiry respective circuits that the half-waves "of current supplied to the track rails by the secondary` winding andmthe rectier'included lin `series `therewith at each end of said section Icannot flow through the4 associated track` relay and "the rectifier included in series therewith but can `4flow through the track relay at the opposite end,

whereby impulsesicf current owalternately to the track relays at opposite ends of said section from Ythe non-associatedtransformers, a check relay for each end of said Asection connected in `multiple Awith the rectiner connected fin `series Vwith the track 'relay `at that end of said section,

a check relay for each end of "said section connected to receiverectied pulsating current from the `secondary Windingof the transformer at that end andconstructed to pick up on pulsating current and drop away if this pulsating current is `changed to alternating currentdue to failure of the rectifier `supplying such" pulsating current, and a signal at each end of said section governing the entrance of'trafc into saldsection at that end and `having a clearing circuit closed only if both of the check `relays at that end assume their manifests clear traillc conditions. c

8,.}In"combination with a ,section of track divided from adjacent sectionslby insulating joints, a transformerhaving aprimary winding and a correspondinglypcledA secondary winding for each "end of said section, a source of alternating current for energizing the primary windings cfsaid transformers with corresponding instantaneous polarities, atrack relay for each end of said sec; tion, three single wave rectifiers for eachendof energized position and the associated track relay i ysaid section, said track: relays; and*v the secondary windings;A of said transformers being correspondyingly connected in multiple-across the track rails and each having one of. said half-wave rectiilers included in seriesy therewith, said rectiers being sopoled in their respectiye. circuits thatthe half- Waves-ofV current supplied to the, track. rails by the. secondary windings. and the. rectersi-neluded. in seriesr therewith cannot. :dow Vthrough the associated track relaysand the. rectiers in cluded in.. series therewith. but soA that 4they can ow through thenon-associated track relays, whereby impulses: of current flow alternately to the trackv relays at. opposite. ends of saidsection from the non-associated transformers,v the third rectifier at eachy end of said section. beingcon.-

-nected in multiple with .the track. relay at that end andV poled to allow the cw of. pulsating cur.- rentf from. theadjacent transformer around said track relay, meansf forvchecking the rectifying effectiveness of. some. of f said rectiflers, and signaling. means controlledby said track relays.. l 9'.. Incombinaton withA a section of track d- Yvided from` adjacent sections by insulating joints,

a. transformer having. a primary winding and a correspondingly poled. secondary Winding. for each.l end of, said section, a track relay for each end of said section, three single Wave rectiers vfor each end of said section, a source of alternating current connected. to energize the. .pri-

that it can ilow through the trad:- relay and rec-` titler included in series therewith atthe other end, whereby impulses of current flow alternately to the track relays at opposite `ends of said section .from such transformers, the third rectifier at each end being .connected in multiple with Athe track vrelayat that end and being poled to .allow the flouri of pulsating current from the adjacent transformer .around said track relay, a l.check relay for checking the Irectifying eiecti-veness oi eaohzot the .reotiers connected in yseries with the secondary windings4 ofsaid transformers, a i

check relay for checking the `rectifying eiectivev.ness of each of the rectiilers connected series with said track relays, and a signal governing the entrance of trahie into each end ofV said vsection each controlled by :the track `relay and two check .relays located at that end.

io. In--combinationA with'a section `oaf track tdivided .from .adjacent sections by insulating joints, a transformer having a ,primary winding .and a correspondingly holed secondary winding fior' each end of said section, a track relay for-each end -oi .said section, .three single waye rectiiers foreach end, .of said section, r.a source -of alterhating current ,tor energizing .the primary windings of .said transformers with corresponding .in-

stantaneous polarities7 said track .relays .andthe .secondary `winding. .of ,said transformers being correspondingly `connected in multiple across the track .rails at each. end of .said .section and each .having one of k,said half-wave. rectifiers .included in series tlierewithso` poled that. the 'half-wave of current supplied to the track rails: by the current ow alternately to1 the track relays at opposite ends of saidsectiony from. such transformers, the third` rectifier at. each end being connected in multiple with the track relay at that end and being poledy to allow the flow of pulsating currentv from the adjacent. transformer around said track relay, a checkv relay for each Y end of said section connected in multiple with the rectifier connected in series with the track relay at that end lot said section, a check relay for each end of said section connected to receiye rectifier pulsating, current` from the secondary winding of the transformer at thatr end and constructed to pick up.v on pulsating current but drop. away it th-ispulsating currentis changed to alternating current due to failure of thel rec.- tiier supplying such pulsating, current, and a signal at each end of said sec-tion' governing the entrance of traiiic into said section at. that. end having a clearing circuit closed only if." both of. the check relays. at that end assumetheir energized position and the associated track re,- lay manifests proceed trafic conditions.

` l1. In combinationwith a section:v of track divided from adjacent sections by insulating joints, a single wave rectifier for each end of said section, a track relay ateach endofjsaid section connected `in series with the. associated single wave rectier' and connected across the rails of that end of said section, .said rectifers being so poled thaty one rectier. allows current vto 4allow polarity relation in series with said another rectifier, Asaid. other rectifiers being sopoled that vcurrent impulses are alternately applied to op- .posite ends of said .sectioneach current impulse being of a polarity so that it cannot .flow through the track. relay and its associated rectifier 'at .thatlerid but can flou .through the :trackv relay and its. associated yrectifier at the other` end, a .check relay connected in .multiple'wi-th each rectifler associated directly with a .track relay, and electro-responsive means .for keach end of said section controlled. b y Vsaid track relay :and check relay for that end. .l v

l2. .In vcombination with a .section of track divided from adjacent lsection-s by insulating joints, a transformer having fafprimary winding and asecondary Winding tor each end :of said section, a source of alternating currentior feuergizing the primary windings of said transformers., .a track relay for each end of said section, two halt-wave rectirlers .for each end of said section, said trackrelays and the secondary of said transformers being so connected in multiple across the track rails and each having one of said half-wave rectiers included in 'senies 'therewith .so poled that 'the half-wave of -cunrent .supplied to the track rails by the secondary wending and .the rectier included in v.series therewith cannot flow through the associated `track relayv and the rectifier` included in seriesv therewith but so that impulses of current iiow alternately to the track relays at opposite ends of said section from such transformers,` a. check relay` for checkingthe rectifying effectiveness of each of the rectiiiers connected in `series with said track relays, and a signal governingthe entrance of traiiic into eachiend ofsaid sections each conlocated at that endl l i t 13. Incombination. with a section of track divided from adjacent sections 1 by insulating trolled by the'track relay and the check relay i joints, a transformer havingV a primary winding `cannot flow through the associated track relay and the rectier included in series therewith but so that impulses of current flow alternately to the track relays at opposite ends of said section from such transformers, a check lrelay for checking the rectifying effectiveness of each of the rectifiers connected in series with the secondary ciated track relay manifests clear traiiic conditlons. i r t A 15.` In a combination witha `section of track divided from adjacent. sections by insulating joints, a source of alternating current, a transformer `having a primaryand a secondary winding for each end of said section and having its primary winding energized from said source,` a polar track relay `for each end of said section, a half-wave rectier for each end of said section, circuit meansfor connecting the secondary windings `of `said transformers and said `polar track relays in multiple across the track rails at each end off said, section with the associated rectifier connected in series with the secondary winding of the transformer and so poled in the circuit means that pulses of pulsating current may flow from each secondary winding through the winding ofthe polar `track relay-at the opposite end of the section ina direction to actuatethe same but not through the winding of the polarrelay at the same 4end of `thesection in a direction to actuate the same, means for .checking the rectifying eectiveness oflsaidrectiers, and a signal at each `end of said section for governingthe movement of traffic into said section controlled by the polar track relay at that end.

1'6. In combination with a section of track divided from adjacent sections by insulating joints, a source of alternating current, a transformer having a primary and a secondary winding for each end of said section and having its primary windings of said transformers, a signal'at each end of said section for governing the `movement i `of traffic intothat end of said section, and means for controlling each of said signalsby the track relay and the check relay associated therewith.

14. In combination with a section of `track divided from adjacent sections by insulating joints, a transformer having a primary winding and a correspondingly poled secondary winding for each end of vsaid section, a source of `alter-l nating current for `energizing the primary windings of said transformers to corresponding relative polarities, a track relay for each end of said section1 two single Wave `rectifiers for each end of said section, saidtrack relaysand the secondary windings of said transformers being correspondingly connected in *multiple across the track rails and each having onelof said halfwave rectifiers included in seriestherewith, said rectiers being so poled in their respective circuits that the half-waves of current supplied to the track rails by the secondary winding and the rectifier included in series therewith at each end of said section cannot flow through the associated track relay and the rectifier included in series therewith but can flow through the track relay` I up on pulsating current and drop away if this winding energized from said source, a polar track relay for each end of said section, a half-wave rectifier for each end of said section, circuit means for connecting the secondary windings of said transformers and said polar track relays in multiple across the track rails at each end of `sa`,idosection with the associated rectifier connected in series with the secondary winding of the transformer and so poled in the circuit means that pulses` of pulsating current from each secondary winding may actuate the polar trackrelay `at the opposite end of said section but can l not actuate thepolar track relay at the same end, a `check relay at each end of said section v connected to be energized from the secondary pulsating current is changed to alternating curi i rent due to failure of the rectifier, supplying such pulsating current, and a `signal at each end of said section governing the entrance of traiiic` into said section at that end and having a clearwinding` of the transformer at that end of said section and to assume its energized position only if such `rectier functions to deliver pulsating current,` and a signal at each end of said section for governing the movement of traiiic into said section at .its end controlled by the polar track relay and the `check relay at that end of said section.

1'7. In combination with a section of track divided from adjacent sections by insulating joints,

`a source of alternating current, a transformer having a primary and a secondary winding for each end of said section and having its primary winding energized from said source, a Vpolar track relay for eachend of said section, a halfwave rectifier for each end of said section, circuit e means for connecting the secondary windings of said transformers and said polar track relays in multiple across the track rails at each end of said section with the associated rectifier connected in series with the. secondary winding vof the transformer and so poled in the circuit means that pulses of pulsating current may actuate the polar track relay at the opposite end but not the polar track relay at the same end, a. check lng circuit closed only if the check relay at that i relay at each end of said section connected to be energized from the secondary winding of the transformerat that end of said section and to assume its energizedposition only'if suchxrectiier functions to deliver pulsating current, and a signal aty eaclsrv .end of .section for, governing the movement of traffic into said section atits end, andr ay :circuit for each signal includinga iront contact of the associated :check relay and controlled by a contact of the associated polar track relay;

18; n combination with a section of track `divided from adjacent track by insulating joints, a l

transformer for each end of said section each having a secondary Winding, a rectiier included in series in each of said secondary windings, a source of alternating current vfor energizing the primary windings of said transformers, the pri- I mary windings of said transformers being energized by( currents of .suon polariti'es yand the' secs ond-'ary Winding and the reotiers being so pol-ed that impulsesA of potential of alternate opposite polarities areapplied alternately at opposite ends Eto tire track rails of saicl'section, a; polarity responsive relay yconnected yacross the rails at'each of the ends of said section so connected that each relay responds only to theV impulses. applied to tlieopposite end of. said. section', means for that impulses of potential ofy alternate oppositer polarities are'appliedl alternately at'opposite ends to the track rails of said section, a: polarity responsive relay connected across the rails'at each ofv the ends of said; section so'connected that each relay respondso'nl'y to theimpulses applied Y to tneonposite end' of` said'` section, a check relay for checking the reotl'fyirig` eiectiveness of each of said rectie'rs: and also controlled by said po'- larity responsive relay, and signaling means controlled by saidA check relay; y

i SEDGWICK N. WIGHT.

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