The "Exposition F lyer" west­ bound ascending th e g rad e approaching signal N o. 353 at left which is equipped with operative grade sig n

~utomatic Signaling and Tunnel Protection

On the Denver & Salt Lake Coded track circuits, up to 11,180 ft. in length, and headblocks located prop­ Denver and from the west, with lines points is SO, but the hor izontal dis­ erly for installation of C. on which the ascending grade would tance is only 38 miles. Starting at the T. C. later-Controll ed not exceed 2 per cent, compensated west end of double track at Ralston, for curva ture. From the west portal Colo., 7.15 miles from Denver and manual block through of the Moffat tu nnel, the Denver & at an elevation of 5,258 ft., the single­ 6.2-mile Moffat tunnel Salt Lake extends westward 72 miles track main line ascends westward at to Orestod and then 103 miles beyond not to exceed two per cent. compen­ to Craig. Also from Orestod, a sin­ sated for curvatu re, for 42.95 miles gle-track line of the Denver & Rio to the east portal. T he 127 curves THE Denver & Salt Lake has recently Grande W estern extends south and in this mileage represent a total of Installed automatic block signaling on west along the Colorado river for 39 5,708 deg. of central angle. The maxi­ 4.7 miles of double track and 47.7 miles.to Dotsero, Colo., where a con­ mum curvat ure is 10 deg. Between Iniles of single track between Denver, nection is made with D. & R. G. W . Arena and Clay, there ar e two 10-deg. Colo. , and the east portal of the line betwee n Pueblo, Colo., and horseshoe curves. I n addition to the Moffat tu nnel, and also, track-err­ Ogden, U tah. Thus, in addi tion to main tun nel through the divide, 29 CUited semi-automatic signaling has trains of the D. & S. L., the line be­ shorter tunnels, ranging from 300 ft. been installed for the direction of train tween Denver and Orestod is used by to 1,700 ft. in length , are located be­ move ments through the 6.2-mile sin­ those tr ains of the D. & R. G. W . tween M.P. 23 and the Moffat tunnel. gle-track Moffat tunnel. which are routed into and out of Den­ . The primary purpose for construct­ ver for direct connections to or from Difficulties of Train Operation Ing the Denver & Salt Lake originally, western points . Including the Moffat tunnel , was to T he territory which was recently In addition to the handicaps of provide a direct route westward from signaled, ext ends from Denver to the grades, curvature and tunnels, train Denver through the Rocky Mountain west porta l of the Moffat tunnel. The operat ion in this territory is all the tontinental divide to western Colo­ elevat ion of the Denver Union Station more difficult during winter months, rado, as well as to points beyond. The and various freight yar ds in that area with moderate snowfall, and tempera­ Site of the Moffat tunnel was chosen is approximately 5.280 ft. above sea tu res as low as 40 deg. below zero F. because of minimum tunnel length level, whereas the elevation of the east Furth ermore, the topography is such Under the divide, with portals at ele­ portal of Moffat tunnel is 9,192 ft . tha t from a practical standpoint , pass­ Vations which could be reached from The mileage by rail between these ing tracks can be located only at cer- J uly, 41 354 R A IL WAY SI GN ALI NG 19

Dwa rf signals 40 and 42 at Zuni where D. & S. L. fre ight trains enter and leave th e mai n line tracks

tected, whereas an ordinary shunt fouling does not provide such protec. tion. The switch circuit controller On each passing track switch does not shunt the track circuit, but contacts in the controller are connected to operate a switch repeater relay. T he signals on this project are of the searchlight type, using the stand. ard color aspects, red, yellow and tain places, with the result that they example, between 10:00 a.rn. and green. The 250-0 ~m d -~ . ope.rating are not equally spaced as to distance 11 :30 a.m., there are four scheduled COli of each searchlight signal IS line or train time. The locations of passenger trains and usually two controlled, thus obviating the use ofa the passing tracks and the capacities freight between Denver and East signal control relay. Except for un­ in terms of fr eight cars are indicated Portal. The Ute, a fast westbound usual instances, to be explained later on the plan. During a 24-hour peri od, Rio Grande frei ght tr ain, usually the aut omat.ic signals are controlledby opposing tr ains are scheduled to make takes siding at Cliff to meet the east- the conventional A.P.B. system to dis.

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Fig. 1- Track an d sig nal plan of the territory betwe> eight meets, and in one instance a ward passenger train No.6, while play positive Stop aspects for oppos­ westward local passenger train takes westbound passenger trains No. 5 ing station-to-station train moves, and siding for a through westward passen­ and No. 1 are closely following. permissive aspects for following train ger train, in the same direction, to movements. Each station-leaving pass. T he operation of extra trains Decision to Install Signaling positive signal which displays the Stop increases the number of meets to be aspect, Code Rule 292, is so designated made. On account of the increasing im­ by a reflectorized sign, displaying the On the ascending grades, the pas­ portance of this Moffat Tunnel route, letter "P," this sign being mounted on senger train speed is about 25 m.p.h. a decision was made to install signal­ the mast below the operative signal and the freight train speed about 20 ing, the first section being between unit. m.p.h. Between Cliff and P lain, pas­ Denver and the west end of Moffat The automatic signals are line con­ senger train speed is limited to 25 tunnel. For the most part, this in­ tr olled in the usual manner, using one m.p.h. and fre ight train speed to 20 stallation is automatic block signaling, control line wire in each direction, in m.p.h. On the 128.6-mile territory but certain features were provided so connection with a common control line between Denver and Orestod, a total that minimum expense will be re­ wire. The shor t track circuits at de­ of 8 passenger trains and at least 12 quired later when changing over to tector sections at switches are of the freight trains are handled daily. Du r­ centralized traffic control. The station­ conventional d-e. neutral type. The re­ ing the peak season of September and entering, station-depart ure signals and mainder of the track circuits, with October, as many as 35 trains have track circuits are located properly for certain exceptions, are the d-e, coded been handled daily. Helper locomo­ future C.T.C. Future OS sections type, using codes at the rate of 75 tives are usually required on ascend­ are provided with one track relay on per minute. One reason for using ing grades for freight trains, and, in the main line, and a second tr ack relay coded track circuits was to minimize order to equalize power, the operatio n on the passing track. Th e signal cir­ the numb er of track circuits ; the of light helper locomotives down the cuits are controlled indirectly by both lengths of these coded track circuits grades increases the number of moves of these relays by means of a repeate r range up to 11,180 ft. A second ad­ to be handled . The periods of maxi­ relay. T he advantage of this arrange­ vantage of the coded track circuits IS mum train congestion usually occurs ment is that broken bonds or broken that, in the future when converting during the forenoon and night. For rails on the fouling section will be de- this proj ect to centralized traffic con- July, 1941 RA ILWAY S IGNA LING 355 ~ I when either the yellow or green aspect is displayed, then through a fr ont contact of A<8 3T P , a series approach Grade ~_--,r------liqhf track relay, to the coils of 1015 and BL to common CL. When the 120 yellow­ 1183TP green repeater relay is released, as a Serie s t rack refc¥y, train passes the signal, the holding ;/ Fig. 2 - Diagr am circuit is through a back contact of of circ uits to con­ YGP, a fr ont of the stick relay, the tr ol a directional coil of 1015 and to CL. This circuit stick IOlY6P obviates the use of contacts in various relays as required in the conventional • stick relay pick-up and hold-up circuit. 8L the downhill end of the passing tr acks to facilitate train movements. Variations in Arrangements of The condit ional feature of this overlap Intermediate Signals is in effect for opposing movements CL ------' but not for following movements. Various factors were involved in deter mining the number and exact trol, the aut omatic control of the sig­ Control of Intermediate Stick Relays locations of the intermediate auto­ nals can be accomplished by track Save Contacts matic signals. As mentioned previ­ circuit code equipment exclusively, ously, the passing tr acks are not and the three line wires, now used for A circuit, designed to reduce the spaced evenly on a basis of distance line circuits, will be utilized for t rans­ number of contacts required, was used or tr ain time. Braking distances for mission of contro l codes and indication for the pick-up and hold-up of the west-bound trains on ascending codes as applied to C.T.C. The auto- stick relays required in the directional grades are entirely different fro m

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Denver and the east portal of Moffat tunnel

matic control of the signals will re­ control of the A.P .B. system. As braking distances for eastbound trains qu ire additional track circuit code shown in Fig. 2, the pick-up circuit for descending the grade. F urth ermore, equipment. 1015 stick relay starts with BL which on account of the mountains, curves feeds through contacts in the search­ and tunnels, intermediate signals had Approach and Successive Approach light mechanism, which are closed to be placed at certain locations to Aspects and Down-Hill Overlaps

For following train movements, the signal in approach to one which is displaying the "Red" aspect, displays the"Yellow" aspect, "Approach." For Opposing trains, approaching a passing track, however, two successive signals display the "Approach" aspect, in ap­ proach to a station-departure signal which is displaying the "Stop" aspect. In the territory involved, the grade IS descending eastward and the east­ Ward station entering signals are nor­ mally overlapped on the downhill side. This overlap is conditional and is on

View of the eas t port al of Moffat tunne l wit h sign als 501 and SOlA 356 RAIL WA Y SIGNAL IN G J uly, 1941 provide sighting distances as long as that signal 211 displays the yellow as­ to display the Stop aspect. On the possible. pect in the usual mann er for follow­ other hand, when an eastbound train T he distance between the west ll1g moves. passes signal 204 at Clay, the West. switch at Plain and the east switch at war d signal 185 at Arena is set to Crescent is 6.5 miles, and three inter­ With no Intermediates display the Stop a?pect. Likewise, if mediate signals are provided for each an eastbound tr am on the passing direct ion. T he distance between the Between Arena and Clay, where no track at Clay throws the switch and west switch at Ley den and the east intermediate signals are used, special clear s the eastward leave-siding dwarf switch at Arena, 4.7 miles, and two signal arrangements are prov ided, as 204A, the signal 185 at Arena dis. plays the Stop aspect. Pla;n - Wes f ~ Operation at Arena -4 ~9 ~ .1 \ This arrangement presents a prob­ lem in getting a westbo und train out 2396P e25 Control 8L of the passing track at Arena. Since Common there is no track circuit on the passing CL tr ack, an overlap into this track for the control of signals 204 and 204A cannot be used. If a westbound train on the passing track at A rena has rights by time-table or tra in orders to depart, a trainman reve rses the switch, which causes eastward station. Fig. 3- Track, signa l and cir­ leaving signal 204 at Clay to display cuit arrangement between pa ss­ ing track layou ts at Clay and the Stop aspect and signal 204A call­ P lai n not be clear ed. Ti me locking is pro­ vided so that the westward leave-sid­ ing dwarf signal at Arena will not intermediates are provided for each clear for 45 seconds after the switch direction. T he distance between the is th rown, which would allow ade­ west switch at Clay and the east shown in Fi g. 4. T he main line with­ quate time for any eastward tra in switch at Plain is 2.9 miles, and one in signal limits at Arena is cut into which may be approaching signal 204 double intermediate location is used. two tr ack circuits, 175BT being the at Clay to stop short of that signal, or, T he distance between the west switch one to the west. Opposite this cut if the train overran the signal, then at A rena and the east switch at Clay section location, and to the right of the controls of westward signals 185 is 10,600 ft ., and no intermediate sig­ nals are used. W here three or two intermediate signals ar e provided for / a "Wesf /trena each direction between passing trucks, Bcrff er y cuf the controls are conven tional. Where e04A>--r 203 /85 f or overlap /75 ~ ~ 17511~ 175fJT only one set of adjacent intermediate I J II r I ~ L 186 ~ ' ~ signals is prov ided between passing ~ tracks, the green indication of the sta­ 804 10,600' ----.:J /7(; tion-departure signal is conditionally 18511 over-lapped through the track circuits 20J 6P WP OTP IB5TP WP . in the limits of the next station layout . As shown in F ig. 3, the control of the coil for the westward statio n­ leaving signal 211 at Clay extends thro ugh contacts of the pole-changer relay of the intermediate signal 225. The control of this 225PC extends through fro nt contacts of the tr ack relay in the station limits at P lain, which constitutes the station overlap. T hus an eastw ard tr ain when occupy­ ing this overlap at P lain causes west­ ward signal 211 at Clay to display the Approach aspect. On the othe r hand, when a westward train occupies the station overlap at P lain, a directional F ig. 4-Track layout an d circuit s bet ween Clay and Arena stick relay shunts out the overlap con­ tacts so that signal 211 displays the the track, is a sign reading : "Signal and dwarf 185A at Arena would be green aspect in the usual manner for Overlap Limits," and rules provide opened by tr ack occupancy. following trains. The stick relays re­ that westw ar d trains which are to U nder the circumstances explained, quired for this arr angement include hold the main line for a meet at Arena when the switch at Arena is thrown, an eastward stick at the east end of are to stop short of this sign, and wait 10 seconds are required to heat the P lain to cut out the green overlap of for the other train. thermal coil of a relay, after which a signal 211, and a westbound stick at If a westbound train passes this time-element stick relay is energized the intermediate signal to shunt out sign and cut section, the eastward sta­ and opens the heating coil. Thirty­ the front contact on the YGP relay so tion-leaving signal 204 at Clay is set five seconds is required for the heat- July. 194 1 RAIL WA Y S IG N ALI NG 357

High signal 185 and dwarf 185A at wes t end of Arena ing coil to cool and close the check contacts. Then the westward dwarf signal 185A will clear.

Grade Signals Controlled Directionally

Each of the westw ard intermediate automatic block signals on the 2 per cent ascending grade is equipped with a "grade" signal, which consists of a normally-extinguished lamp unit, with a standard sized background, mounted on the mast 6 ft. below the main searchlight signal unit. The cover glass of this "grade" signal has the letter "G" etched in the surface, and, when operative, displays a yellow light to outline the letter "G". A grade signal is lighted only when a westbound train is occupying the he is to pick up orders at the station resistor from one cell of storage bat­ block controlled by the signal, and and may hold the main line. Thus tery. The coding is accomplished by when the main unit is displaying these "advance" train-order signals an oscillating type code transmitter, the Stop-and-P roceed aspect. Th e which are used at seven locations, are which is a device const ructed some­ "Stop-and-Proceed" aspect and the an important factor in reducing un­ what on the principle of the balance grade light authorize a following necessary tr ain delays. An important wheel of a watch. On a vertical shaft, westbound train to pass the signal at point, with reference to the advan ce there is an arrangement of weights a speed not to exceed 8 rn.p.h, with­ tr ain-ord er signals, is that they are and a coil spring such that the shaft out stopp ing at the signal. T his rul e mounted 6 It. below the automatic rotates back and forth 120 deg. of applies to passenger as well as freight signals, so that there can be no con­ revolution, with 75 operations clock­ trains. The control of the grade sig­ fusion between the aspects of auto­ wise and 75 operations counter-clock­ nal is directional, i.e. for an opposing matic and the train-order signals. wise each minute. Normal variations train, the "grade" lamp is not lighte d. At most train-order offices, indica­ in the voltage of the operat ing battery This featu re is accomplished by ex­ tors are provided to warn the oper­ do not affect the period of oscillation tending the control thro ugh contacts ators of the approach of trains from of the code transmitter. of a directional stick relay. either dir ection. Three indicators of Each code transmitter is in opera ­ the enclosed disk type are provided in tion normalIy, motion being initiated Advance Train-Order Signals each office. One indicator displays and continued by energization from a red spot aspect when a train is oc­ the 8-volt coil of a magnet which At some layouts, such as, for ex­ cupying the track circuit in app roach rotates the shaft to the ext reme clock­ ample, Cliff, the tr ain-order office is to the westward station-enter ing sig­ wise position, at the same time wind­ located a considerable distance from nal, and a second indicator displays a ing the coil spring. When in the clock­ the east switch of the passing track. red spot aspect when a train is occupy­ wise position, contacts are closed to Between the switch and the office, the ing the track circuit in approach to the feed the current impulse to the rails, track curves around a bluff so that the eastward station-enter ing signal. and likewise the circuit for the oper­ train-order signal cannot be seen by These track circuits range from 1.5 ating coil is opened so that the coil the engineman of a westbound train to 1.75 miles in length. A third indi­ spring takes effect and rotates the until he is within a few hundred feet cator in each office can be connected to shaft to the counter-clockwise posi­ of the office. W hen the operator either east or west signal control tion, at which location contacts shunt has orders for an approaching west­ thro ugh a double-pole, double throw the track circui t for 0.4 seconds. In bound train, and sets the train-order switch, operated by the operator. the meantime, the contact in the oper­ signal accordingly, a yellow lamp is W hen this indicator displays the red ating coil circuit has been closed, and, lighted to outline a letter "T" in a spot aspect, the operator knows that a as soon as the force of the spring is normally-extinguished signal unit train has passe d the station-departure spent, the force of the magnet swings which is mounted on the mast of the signal at the next town adj acent to the shaft again to the counter-clock­ West-bound station-ente ring signal at him. The indicators at each office are wise position. the east switch.T he "T" aspect will fed from a set of five cells of 500 a.h. T he rail joints are bonded with rail­ not be lighted unless the main signal primary batt ery. head bonds. On about half the mile­ unit is displaying a yellow or a green age, Raco mechan ically applied bonds aspect. When the westbound "ad­ Operation of Coded-Track Circuits are used, while on the remainder of vance train-or der" signal is lighted, in Automatic Signaling the terr itory the Cadweld welded the east bound ente ring signal auto­ bonds are used. At the relay end of maticalIy goes to stop. W hen this "T" The code for each track circuit con­ each coded track circuit, a O.1 -ohm aspect is displayed, the engineman of sists of impu lses 0.4 seconds long of relay is connected to the rails. A two­ a train has adva nce inf ormation that direct current fed th rough a series point relay is used where track cir- 358 RAILWAY SI GNA LI NG July, 1941 cuits do not exceed 7,000 ft. in length enter the tunnel. In the new signaling one train movement at a time through and a one-point relay with a two-point arrangement as shown in Fig. 6, the tunnel. T he operation of two 140-ohm code-repeater relay is used searchlight type signals direct tr ains to trains in the same direction in the on longer track circuits. When the enter and use the tunnel. These sig­ tunnel at the same time is not prac­ track circuit is not occupied, the track nals are controlled automatically by tical, not only on account of the effects relay is energized and released 75 track circuits throughout the length of locomotive smoke on engine crews but also due to the fact that engine men could not, under all conditions see the signals due to the density oi IMFD IZ w smoke and fog. The signaling, there_ 1.5W fore, is set up for a full length, track_ GL circuited control, absolute block, East P ortal to Winter Park, or Winter CL Park to East Portal. BL IMFD BL _ / : 12w Operation of the Control Machines

A miniature-lever control machine F ig. 5 -Diagram of the coded track cir­ is prov ided at each of th ese offices. By cuit control of the means of a buzzer code, the two oper­ ~I DT P _ si gnals ators can coordinate their controls Drp Relay is ope rcded on ly --38 wSlow release when a train is to be operated through f rom enerqy Induced In s econda ry of transformer the tun nel. The buzzer controls are on a special simplex circuit which was superimposed on the existing tele­ times each minute to follow the code. of the tunn el and also manually by phone line circuit. F or example, if A fr ont contact of this TR relay com­ cooperation on the par t of the oper­ signal 501 is to be cleared for a west­ pletes a circuit for the coil of a re­ ators at East P ortal and Winter Park. ward train, both opera tors set their peater relay T PR, rated at 140 ohms. The switch at the west end of the respective "T raffic" levers to the west­ As shown in Fig. 5, the "upper" finger passing track at East Portal is oper­ bound position. The result is that in the TPR relay feeds direct current ated by a lever in a mechanical inter­ code is fed to the track at the west end, to first one and the other of the two locking machine, and a second lever Winter Park, and is repeated through primary coils of a transfo rmer, at the is used to operate a facing-point lock fr om one track circuit to another to rate of 75 per minute. The "bottom" on this switch. Signal 501 controls decoding equipment at East Portal, finger of relay T PR acts as a mechan­ ical rectifier to take the energy from the secondary of the trans former and Winfer Par k produce uni-direction impulses of -- Wesf direct current at the rate of 150 per minute, which serve to pick up and /». hold the 38-ohm DTP relay in the 56 6~ so;r...- BnA energized position, so long as code is '-Refuqe 19 50Z being received at the rate of 75 per Pig, 6-Signaling th ro ug h Moffat tunnel minute by the code-following track relay TR. Th e signal circuits check westward moves on the main line thus energizing a relay which lights the contacts of relay DTP, in the fro m this signal through the tunnel to a lamp to indicate to the operator that usual manner. Steady curr ent to hold Wi nter Park. If the switch is re­ traffic is established westward. T hen relay T R energized, will not result in versed, signal SOI A controls westward he can operate his signal lever to clear relay DTP being energized because moves from the passing track through westward signal 501, and the signal of the arrangement of connections to the tunnel. At Winter Park, the will clear, providing the coded control the transformer. switch at the east end of the passing from the west end is still being re­ Capacitors as well as resistors are track is hand-thrown. T he eastward ceived at East Portal. On the other connected across the primary coils of signals ar e 566 and S66A to control hand, if traffic is to be established the transformer, to reduce arcing and moves through the tunnel to Ea st eastward, both operators set their radio interference at the contacts of Portal. traffic levers in the eastbound position, relay T PR.Also, resistances are used The signaling is arranged to handle and code is fed fr om E ast P ortal across the coils of relays TPR and DTP . Tra ffic Direction Signaling Through the Moffat Tunnel

Formerly the train movements through the single-track Moffat tun­ A spring switc h nel were directed by absolute manual layout showing the block, between the office at East P ortal plates and the rai l and the offi ce at Winter Park, which bra ces is 3,000 ft. west of the west portal. Th e operators at these stations worked under the direction of the dispatcher when clearing their respective manual block signals to authorize trains to July, 1941 RAI LWAY SIG NA L IN G 359 through the track circuits to W inter following track relay induces a cur ­ effect of the ballast resistance to in­ park, so that an eastward signal, 566 rent to flow through the coils and the crease the release time of a relay or 566A, can be cleared by the oper­ ballast. This action retards the release brings about a total effect that, in half ator at Winter Park. of the relay. Thi s effect, however, was the distance through the tun nel, the Normally, the track coding equip­ overcome by using code that is effec­ code is converted to about 1 sec. on ment is not in operati on, and can be tive for only 0 sec. to energize a re­ and 1 sec. off. At the mid-point in set in operation to be effective to clear lay,and is cut off for 10 sec.to permit the tunnel, i.e. the apex, there is a release of the relay. T he code trans­ decoding and recoding station. The mitters are of the oscillating type, and incoming track code to the apex sta­ Trac k CK TB Track CK TII operate 60 times per minute. The pro­ tion operates a code-following trac k ducton of code, which is feeding for relay, as shown in Fi ~. 9. When thi s o sec. and off for 10 sec. is accom­ relay is energized by the first incominz plished, as shown diagrammat ically in impulse, a relay FP, "front contact" F ig. 8, by a code transmitter and two repeater, is energized, and due to it, code-following relays. slow-release chara cteristics it remains T he code transmitter CT, swings energ ized as long as it gets an impulse to the right for 0 sec., and then to the of current every two seconds. When left for 0 sec.Relay CTI picks up the code-following track relay re­ with the first right swing of the code leases, with relay FP up, a circuit is 1.2 tij I.Z tij transmitter. W ith CTI up, the first closed to energize " front-back" re­ left swing of the code transmitter peater relay FBP, which likewise has causes relay CT2 to be energized. slow-release characteristics so that it W ith CT 2 up, the next right swing F ig. 7-Cut sectio n in tunn el remains up as long as it gets an im­ of CT shunts the 125-ohm resistor in pulse once in every period of two sec­ the CL lead of relay CTI and the onds. W ith both F P and F BP picked a signal, only when fed all the way relay drops. On the next left swing up, a circuit is closed from battery to through from one end of the tunnel operate an oscillating code transmit­ to the other. Thus the two rails, when ter which, in combination with a set not occupied by a train, are used as of cn, CT2 and CPR relays, as ex­ conductors to transmit coded energy. CT plained previously, causes coded With any track circuit occupied, no energy, 0 sec. on and 10 sec. off, signal can be cleared to authorize a to be sent out on the rails to be re­ train to enter the tunnel at either end. peated through the track circuits and As shown in Fig. 7, each of the cut section repeaters to the far end code-following track relays is nor­ of the tunn el. The one code transmit­ mally de-energized, and the coils of CT! ter at the apex station produces a code relay B, for example, are connected for either direction, depending on the through back contacts of relay A to controls established by the code com­ the rails of track circuit B. When ing into this location. coded energy comes in from the west This code transmitter as well as all on track circuit B, relay B is energized CT2 the relays are normally de-energ ized. and released to follow the code, but At each cut section, as well as at the relay A remains de-energized. apex location, a set of two 500-a.h. Energy fr om a set of two cells of primary cells in multiple provide primary battery in multiple feeds energy to feed direct current for the thr ough fro nt contacts of relay B to CPR coded impulses to the track in each send impulses of energy on eastward direction. Th e code transmitter and over track circuit A. If relay A is various control relays at the apex loca­ operated by code coming in on track ~--+2 Sec nds -1------';>-1 tion are fed from a set of 16 cells of circuit A, the reverse operation takes F ig. a- Code pro ductio n 500 a.h. primary battery. T hus all of place. Thus two relays and two sets the electrical energy required inside of battery are required at each re­ of the tunnel is supplied fr om primary peater track cut location. of CT , CT2 drops and CPR picks batt eries, so that no power distribution up, energizing the track for 0 sec. circuits are required. Th erefore, the Low Ballast Resistance On the next right swing of CT the only wiring for the signaling system 2-sec. cycle starts over again. inside the tunnel includes connections Except where insulated joints ar e As this code is repeated through the from the rails to instrument cases and required, the rails are welded together track circuits and cut sections, the battery boxes, as well as wiring inside throughout the length of the tunnel. For this reason, bond resistance is not a factor. However, due to the FP dampness, locomotive smoke, cinders and salt brine, the ballast resistance is extremely low, ranging from 10 to ~FB P as low as 0.5 ohms per thousand track feet. For these reasons, the tr ack in ----CL the tunnel was cut to make 10 coded "'-.: track circuits, maximum length 4600 ft. On account of the low ballast re­ ~ sistance, when the energy of a code CL- - I 1------., flL--- BL impulse is cut off, the collapse of the Cod e from smiHer magnetic flux in the coils of a code- F ig. 9-Decoding at apex in th e tunnel 360 RAilWAY S I G NA LI NG July, 1941 these housings. Cast-iron relay cases Ea st Portal causes an AR relay, in provides "distant" signal aspects for were.used, and we~e coated with pitch series with the battery being fed .to signal 502A . Signal 504 display s a to mrmm rze corrosion. that track circuit, to be coded, which green aspect only if 502A is yellow or picks up an "AR" stick relay, and this green, and 504 displays yellow if Signals in the Tunnel relay sticks up through a back contact S02A is red. Signal 504 does not dis­ of the FP relay, which is one of the playa red aspect. As a warning to In side the tunnel the grade ascends decoding relays for a westbound code enginemen of trains in the tunnel, that at 0.3 per cent from East Po rtal to the fr om East Portal and is de-energized they are approaching a portal, a center of the tunnel, and from there as soon as the head end of the train special dwarf signal is located 1,750 the grade descends westward at about passes the apex. W hen the helper ft. from each end. Such a signal is 0.8 per cent to the West Po rtal. passes beyond the apex, the FBP re- controlled to flash a white light 30 Helper locomotives are not required in the tunnel for westward trains, but a helper, usually coupled at the rear , is required on each eastward tonnage fr eight train, between 'Iii/inter Park and the apex of the tunnel. After passing the apex, the train is stopped, and two minu tes are allowed for un­ coupling the helper , then the trai n pro ­ Panel of control ceeds. machine in office From the controls explained previ­ at East Portal ously, obviously no second eastward train could get. a signal to ente r the tunnel until both the helper and the leading eastward train have departed from the tunnel signal limits. Thus, a westward dwarf signal at the apex location, to autho rize the helper loco­ motive to return from the apex to W inter Park can be controlled sep­ arately from the over-all end-to-end tunnel control. After an eastbo und lay for the eastbound code from Win­ times per min ute as a train ap­ train with a helper on the rear has de­ ter Park picks up, and in turn picks proaches. This control is accom­ parted from W inte r Park, the oper­ up a GR relay which causes th e west­ plished through the track circuits ex­ ator sets his traffic-direction lever at ward dwarf at the apex to display a plained previously by use of a re lay in series with the tr ack feed. The switch at the west end of the passing track at East Portal is oper­ ated by a two-lever mechanical inter­ locking machine. As exp lained previ­ ously, a miniatur e lever machine in the East Portal office controls the traffic direction as well as the two westward tu nnel entrance signals 501 and SO IA. T his same machine also controls th e eastward two-ann dwarf signal 502AB , which is just inside the tun­ nel, for directing eastward trains on the main line or into the passing trade Th e switch at the east end of thi s passing 'track as well as the crossover between the main line and this pass­ ing track are all hand-thrown. The westward signals for the main line and ~"~ for take -siding at th e east end of the passing track are controlled by the miniatur e lever machine in the East i1r---:J--~ Po rtal. F ig. lo-Cir cuit s at r ef­ Ralston, West End of Double Track uge 9 in th e tu nn el The switch at the west end of Rals­ ton, which is the west end of double the westb ound position, which causes yellow aspect. This authorizes the track, is equipped with an oil-buffer the code to be sent out on the rails helper to return to Winter Park. This spring mechanism. Eastward signal eastward toward the rear of the de­ dwarf signal is normally extinguished 72, normally displays a green aspect parting train. for throug h westward moves, and dis­ to govern tra in movemen ts on the As shown in F ig. 10, when the head plays a "yellow" aspect only under the diverging route over the No. 18 tu rn­ end of the train occupies the last track circum stances exp lained previously . out to the righthand eastward track, circuit in appr oach to the apex loca­ Eastward dwarf signal 504, located the spring switch being set norma lly tion, the code sent westward from 900 ft. from eastwa rd signal 502AB, for this route. Westward autom atic RAILW A Y SIG NA L IN G 36 1 july, 1941 . nal 71 normally displays the green lined normally for the diverg ing route sig ct for the Ralston-to-Leyden to the left, as approaching from the asP~a ll block for opposing moves, or west, this being the track lineup used ovepermissive aspect for following by Rio Grandepassenger trains enroute 1 from and to the Un ion Station. The estbound train movements . wAt Zuni, a turnout equipped with a straight track, from Fox J unction ing switch mechan ism, exte nds eastward, leads to the D. & S. L. pas­ :P~ 111 the westward main track to the senger station. Normally the signals. ~ & S. L. freight yard. T his lead is 15 and 15A, as well as the top arm 'ed by freight tra ins of that road of 16A-B, display proceed aspects. All ~ hen enten.ng orl eavmg' the mam . westbound trains of both the D. & IV e The westward main line signal S. L. and the Rio Grande stop for I 4m1is· normally clear. W hen the opera- orde rs at P rospect, one-half mile east torat Zuni wants to line.up for a west­ of Fox Junction. As a westwa rd tra in. bound D. & S. L. frei ght to depart for exam ple, on the D. & S. L. ap­ from the yard, he throws a kni fe proaches Fox J unction, approach switch, which causes signal 41 to dis­ track circuits are shunted which set lay the Stop aspect, and signal 41A signals 16A-B as well as 15A at the foclear, if the track ahead is unoccu­ Stop aspect. Likewise, a Rio Grand e ied . Eastward two-arm dwarf sig­ westbound trai n would set 16A-B and ~al 42A-B normally displays a green 15 at the Stop aspect. When an east­ aspect in the top arm. W hen an east­ bound train approaches F ox J unction, bound D. & S. L. freight train is to signals 15 and 15A are set to display move into the yard, the crossover is the Stop aspect. reversed, and the dwarf 42A -B dis­ plays an aspect o.f red.-over-yellow, Power Supply a nd Pole Line while at the same tune, signals 41 and Signal N o. 16 at F ox Junction 41A display the Stop aspect. A new crossarm was installed on At Endo, which is the east end of each pole of the existing pole line. ar y cells used in the tunn el signaling. double track, both switches of the T his arm carr ies th ree No. 8 wires ar e rat ed at 500 a.h. Edi son primar y crossover are equipped with oil buffer for the control of signals and two No . cells are used with the exception of spring mechanisms, and the switches 4 wires for the 5s0-volt, single-phase , those on the tr ack circuits in the tun­ are lined normally fOJ- a westbound 60-cycle, power distribution. The nel which have AR relays in series, train to be diver ted fro m the single wires are har d-drawn copper with LeCarbone 619-A air -depolarized track to the double track. T he tail weatherproof covering. At each loca­ cells being used on these circuits. track, which is an extension of the tion, a 0.25 kv.a, 550-110 volt trans­ The automatic block signals are westward track to the east, is the lead former is mounted on the cross-ar m. normally lighted thro ugh transform ­ used by Rio Grande freight trains Low -voltage trans form ers in the in­ ers from the a-c. power, but, if this when entering the westward main strument housings provide voltages supply fails, the signals are lighted track. Signal 26 and signal 23 at for feeding the signal lamps normally from the storage batteries, using ap­ Endo normally display proceed and for operating rectifiers for charg­ proach control circuits . Various ap­ aspects on auto matic control. ing storage batteries, which are rated proach lightin g schemes are used, such The east end of the new installation at 80 a.h., and are the Exide T ype as, contacts in track relays, series line is at Fox Ju nction , located about 1.5 D MGO -9. F our such cells are pro­ relays and series track relays. With a miles west of the Denver U nion Sta­ vided at each signal and one cell feeds train on a passing track such as at tion. T he switch at Fox J unction is each tr ack circuit. T he primary bat­ Leyden, the ord inary approach control equipped with a spring buffer oper­ tery used to feed the indicators at the lighting would not be effective to light ating mechanism, and the switch is train-order offices, and also the pnrn- signal 129.In such instances, the equivalent of approach lighting is effected by a small switch in the tele­ phone booth, which is operated by a trainman when the train is read y to depart. Th e grade signals are fed fro m battery, with a cont rol circuit as shown in Fi g. 2.

Instrument Houses

At each end of each passing track, At the interm edi­ a 6-f t. by 8-ft . welded sheet-metal ate signals th e r e­ house includes the relays, rectifiers, lay and batte rie s are housed in big batter ies and other equipment. Ade­ sheet-metal cas es quate space is prov ided for additional relays and batteries when c.T.c. is installed. The outer door of each house leads to an entry way, with a second door leading to the interior of the house. This entry way serves as a telephone booth, the outer door be­ ing locked with a switch padlock and the inner door with a signal lock. At (Continued on page 367) July, 194 1 RAI LWAY SI GNA LING 367 . 3ting "flipping," false closed and sists o t eight cells of Edison _'\4H. switch circuit contro llers are equipped 111 n COJltact~ and other trouble, the nickel-iron-alkaline, rated at 12 volts. with spring devices which, in case the oP\ rca,on for which this type of 100 a.h., 011 floating charge trom a connecting rod becomes disconnected, ~~Y5 were provided in this ius.talla- l.'rion RT-42 copper-oxide line rccu will operate th e con troller to the cen­ r. The track relavs are at the f er Track circuits on the • TickL ter position. T he cables f rom a switch !Ion. 50 -: h f f 4- hOI, P. T_ type, WItI tour ront- Plate Me straight primary battery fe'l circuit controller extend through a Rlur back "n.d ('i.t:ht f~~nt-eight back hv th ee eel, of Edison Type 1002 section of discarded air hose and dow n ntact co'nbtl' mons. I he line relays 1000 a h nr imarv battery ill mul ;pl1 into the ground. A special fitting is ::,0. 11m, F'. T -50 type with the ar "- .' ' I'rack c rei.its OIl the DT . " r. are provided on th e case of each switch rne COl act c ubinatic 1> as the ''''CK a c. ')rill1"r , fe

T~-- J L~, , -~-~ Signaling on the Denver & Salt Lake

( Continue d from page 361) the interm ediate signal locations, the relays and batteries are hous ed in large-sized, double-door, shee t-metal WIring at rear of relay panel cases. The terminals, fu sed cutout s, bootleg outlets and various oth er ac­ r- _ ----< ...... - -1 this installation, a few of which are cessories on thi s installation wer e __- 1 r - _ --- ~ also located III the house, include furnished by the R ailroad Accessories r - ...... r -_ -- - ~ DN-ll track, DP-~O track, DN 18 Corp oration. The in sulated wires and ,.. -- -- - ~ N!--orma/- Trans it Revers e line, DX-13linc, DT-lO line, ANL+O cables are of K erite manufacture, power off and DN-22-P power off outer covering of th e un derground F ig. ll-Controller connections relavs, cable is of the mummy type, with no at a spring swit ch All of the underground cables en­ metal. Sections of 4-in. fiber conduit tering the house, which are K critc were installed in th e concrete found'a­ . controllers is shown in Fi g. 11. If th e parkway with murnmy finish and no tions when they were poured in place. norma lly-closed switch poi nt is open metallic content, are terminated on a T he cab les are brought up th rough more than 34 in. or if the normally­ terminal board behind the relay rack. these conduits into the cases or houses. open switch point is open less than Each cable is pot-headed and the in­ At signals, th e cables extend up 3-in ., th e relay is released. In order rlividual conductors extend to stand­ through the masts, and , near the top, fo r th e relay to be energized to repeat ar.] Raco terminals, 1ro111 which point out through fittings to the searchlight the rever sed position of the switch other conductors are distributed to the units. when hand-thrown , the normal point relay :0 ket where thev are soklere 1 The rail through this territory is must be open at least 3 in., and the h place, - 100 lb., and Rail Joint Company reverse point must be closed within armoured type insulat ed joints are 34 in. of the stock rail. Power Supply used. Each hand-throw switch is T his installa tion was installed bv equipped with one l -in , by 8-in. in­ the D . & S. L forces under th e juris­ Commercial i)OW I' at 110 volts. 60­ sulated gage plate, with adjustable rail diction of B. W. Molis, sig nal engi­ CYcles, a-c , is received at the crossing braces, and each spring switch is neer. The maj or items of sig nal The main operatmg battery at the equipped with th ree insulat ed gage equipment wer e furnished by the Gen­ ero-,iug for relays, signals, etc., con- plates and adjustable rail braces. The eral Railway Signal Company.