307

Southward signal at the north end of the sid­ ing at Buchanan, Va.

Project on 107.8 miles of single track and 10 miles of double track reduces delays on busy line handling 45 to 55 trains daily

and-south direction between Roanoke, Va., and Hagerstown, Mel. At Ro­ anoke, connections are made with the east-and-west main line of the Nor­ folk & Western between Cincinnati and Columbus, Ohio, and Norfolk, N. &W. Va., as well as with a line between Roanoke and Winston-Salem, N. C. At Hagerstown, connections are made with the Pennsylvania and the West­ ern Maryland, at Shenandoah Jct ., with the Baltimore & Ohio, and at Installs C. T. C. Waynesboro with the Chesapeake & Ohio. Prior to the war, this Shenandoah On Shenandoah Valley Line District handled two passenger trains and three through freight trains each way daily, in addition to local freight trains. In February, 1939, the last THE Nor folk & vV estern has recently well as on 107.8 miles of single track. pre-war February, this district completed an improvement program T he purpose for these improvements handled 91,213,000 gross ton miles. on the Shenandoah Valley District, was to reduce train delays and to in­ At that time, the freight traffic was including the construction of second crease the operating capacity approxi­ mostly agricultural and manufactured track on 10.56 miles, and the installa­ mately 30 per cent. products, with no coal except for local tion of centralized traffic control on This Shenandoah Valley line ex­ delivery. By February, 1942, the this new section of double track as tends 238 miles in a generally north- traffic had increased to 180,452,000

Control machine for the Roanoke to Stuarts Draft section is arranged . in a "U" shape June, 1944 RAILWAY SIGNALING 308 dispatchers could not issue ord~rs fa.st miles of the single track in the sec­ gross ton miles, nearly double that enough, and as a result ~rai;ns, m tions where grades and curvature re- . for February, 1939. Next came the rnany instances, would walt m the duced the train speeds. One section war and curtailment of vessel mo-ye­ yard for orders, or ":'ould be st?pped of C.T.C. extends 85 miles between ments along the Atlantic Coast, which necessitated that much of the co.al, at stations on the lme to wa1t for North Roanoke and Stuarts Draft which had been moved by coastwise orders. Inferior trains were required and the second section extends 34 vessels north from Norfolk, Va., be to clear the main line at least five miles between Shenandoah and Ben- . handled by rail. As a result, the minutes prior to the schedule time of tonville. traffic on the Shenandoah District in­ superior trains. If some trains did creased to 558,557,000 gross ton miles not make the time anticipated, other Physical Characteristics of Line in February, 1943, more than six trains would be delayed because there times the pre-war figure. was no means for changing train or­ The track· consists of 130-lb. rail This traffic included 22,591 loaded ders soon enough to take advantage good ties and crushed rock ballast' cars and 1,139 empty cars out of of the changed conditions. all of which is maintained in good Roanoke northbound, 16,201 of the Especially on the heavy grades, the condition. The maximum permissible loaded cars being coal, and 5,472 trains lost a great deal of time when speed for freight trains is 45 m.p.h., loaded cars and 13,736 empty cars into Roanoke from the north. The peak day was February 23, 1943, when 1,223 loads and 62 empties were moved north from Roanoke, and 276 loads and 715 empties arrived at Ro­ anoke from the north. During the last few months traffic has decreased slightly, a total of 42,117 cars, count­ Equilateral turn­ out at the end of ing both out of and into Roanoke over double track near the Shenandoah District, being Cold Spring, Va. handled in February, 1944, as com­ pared with 42,938 in February, 1943. The traffic in February, 1941, in­ cluded an average of 14.4 trains daily as compared with an average of 33.3 trains in February, 1944. These fig­ ures include four passenger trains daily and a local freight train each way daily except Sunday, as well as entering or leaving the passing tracks and on grades, either ascending or return moves of light helper engines. at which hand-thrown switches were descending, the limit is 30 m.p.h. ~he Prior to the recent improvements, in service. T herefore, a decision was maximum speed for passenger trams train movements were authorized by made to construct second track on is 65 m.p.h. timetable and train orders, with auto­ 10.5 miles of the heaviest grade be­ Between Roanoke and Buchanan matic block signal protection. As the tween Vesuvius and Cold Spring, and the railroad passes over the divide be­ traffic increased during 1942, the de­ to install centralized traffic control on tween the Roanoke and the James lays to trains became excessive. The this double track as well as on 107.8 rivers, the ruling grade southbound is 1.5 per cent for 3.5 miles between mile posts 221 and 225. On this grade there are three 4-deg. curves, one 5- deg., one 6-deg., and two 7-deg. The tonnage rating for Class Y-6 locomo­ tive southbound up this grade is 2,650 tons. As the majority of southbound traffic consists of empty cars, the train length, rather than tonnage, usually determines the limit. Between Buchanan and Glasgow, 19.2 miles, the line is near the James river and is mostly at river grade. Between Glasgow and Buena Vista, Typical signals at the line follows up the valley of the the north end of Buena Vista, Va. North river at water grade. Between Buena Vista and Stuarts Draft, 32 miles, the line passes over the divide between the James river and the Shenandoah river, the maximum grade northbound being 1.5 per cent for about 1.25 miles between M.P. 162.6 and 164, this being the ruling grade northward. The crest of this grade is at Lofton, and the ascending grade southward from Cold Spring to Lofton is about 1.5 per cent for nearly three miles. The curvature on this grade, however, is very light, so June, 1944 RA ILWAY SIGNALING 309

Pktn Lofton Cold Spnng p~. ,' Q9e,....<.S'.)( _,' a£1:.,., ~ ,, ~ ~~~~ ~~------+------~~~---- , ""1 I , -;:--7<-o""R-oa""n""o.,.ke---+1-----<,_"f...:: '"':...-----l------::t ---T:Hagersfown ~ ,, 11~ ~ ~'"~Y ~ ~ ,, ,, ,, ,, ,, ,, ,I Loch laird ,, I ~ , ~ To Lexinqfon - LJ__, ,I ,, I ~~~~~------~~~------~~ ,, r-n ~ ~ ~ To He~ qersfown - ,, I _.... To Roanoke []3--fl ,, Buena VtsfaJ , • ~"X 00'"""/...::; <"

C.IC. Ter r ifory , J'.?, , <"~ Time fe~bl e Clnd ------, ~,~ fre~in o rder ferr ifory ,II OQ"-? ,, ,, ,,. ,, ,, ,, ,, ,, I ,I Typ ical le~youf of various I ~fions according fo legend •

Glasgow ~ lib ~ ~---1 ------~... ~~~~------~, ---~~/"~~------~~~==~~------~~~~~T<~o7.H-aq-e~+own""" -

-To Ro"nokell ,.··v)"/'c::,y/;;01

Diagram of the division showing the C.T.C. territories and typical track layouts 310 RAILWAY SIGNALING June, 1944

Hand-throw stand with an electric lock on an out­ lying switch in C.T.C.

northbound and 3,000 tons south­ bound over these ruling grades be­ tween Shenandoah and Hagerstown. For trains handling more than the rated tonnage, helper locomotives are provided for northbound trains be­ tween Ingham and M.P. 98. Thus on account of the grades and extra helper locomotive moves, centralized traffic control was installed on the 34 miles of single track between the north yard switch at Shenandoah and the north passing track sw~tch at Ben­ tonville. These new facilities include that this is not the ruling grade south­ of double track. Branch line trains semi-automatic signals and power bound. The new section of second of the Chesapeake & Ohio, one each switch machines at the north yard track extends throughout the heavy way daily, use the Norfolk & Western switch at Shenandoah and at the pass­ grades between Cold Spring and main line between Glasgow and Loch ing track switches at Ingham, Stanley, Vesuvius, 10.5 miles. Laird. The junction switches at Luray, Vaughn, Rileyville and Ben­ The Class Y-6 compound mallet Glasgow and at Loch Laird, as well tonville. locomotives, with 152,206 lb. tract­ as a crossover between the main line ive power simple and 126,838 lb. and siding at Glasgow, are power­ C.T.C. Control Machines compound, are rated at 3,000 tons operated and included in the C.T.C. northbound between Roanoke and In the track layouts at the ends of The dispatchers' offices for the en­ Shenandoah, this tonnage being de­ double track at Vesuvius and Cold tire Shenandoah District are located termined by the ruling grade previ­ Spring, the switch points are 30 ft. in Roanoke. One dispatcher operates ously discussed. The operating prac­ long and the frogs are No. 20 with the the C.T.C. machine for the North tice is to handle about 6,000 tons in divergence divided to make equilat­ Roanoke-Stuarts Draft territory and each train, with a Class Y-6 helper eral turnouts. Therefore, a train handles the Stuarts Draft-Shenan­ locomotive at the rear just ahead of movement from the single track to doah section by train orders. A sec­ the caboose. From 70 to 75 cars of either track of the double track or ond dispatcher, in a different room, coal, or about 100 cars of mixed vice-versa can be made at normal operates the C.T.C. machine for the freight, made a train of 6,000 tons. speed. At these locations the freight Shenandoah-Bentonville section and The helper locomotive is included in train speeds are limited by the grades, handles the Bentonville-Hagerstown the train when it is made up in the but passenger trains are authorized to section by train orders. yard at Roanoke and runs through operate through these turnouts at The Shenandoah-Bentonville con­ the 76 .6 miles to Lofton. After pass­ normal speeds up to 65 m.p.h. trol machine consists of a panel 60 ing the crest of the grade at Lofton, Between Stuarts Draft and Shen­ in. long, as shown in one of the ac­ the train is stopped with the rear just andoah the line is located in the val­ companying illustrations. T he Ro­ north of tne wye switches. The helper ley of the Shenandoah river, the anoke-Stuarts Draft control machine locomotive is cut off and is turned on grade as well as curvature being com­ is made up of five panels arranged the wye, while the caboose drifts on paratively light. In this section, train in a horseshoe shape, as shown in a down and is coupled to the rear of movements are authorized by time­ picture herewith, the total length of the train. Then after the train de­ table and train orders, with automatic the panel being 15 ft. parts, the helper returns light to signal protection, the same as pre­ A special feature of the illuminated Roanoke. Thus for ev-ery tonnage viously. track diagrams on these machines is train northward, there is an extra that a track occupancy lamp is pro­ light-engine movement southward be­ The Shenandoah-Bentonville vided to repeat each and every inter­ tween Lofton and Roanoke, which Section mediate automatic block, this practice was an additional consideration in made it necessary to use longer sec­ favor of providing centralized traffic Shenandoah, 135 miles north of tions of diagram to represent the por­ control all the way between Roanoke Roanoke, is the sub-division point at tions of single track between towns. and Stuarts Draft, which is the first which engine crews and freight train A result is that the levers are spaced siding layout north of Cold Spring. crews are changed. For the 105.7- farther apart in some instances than This C.T.C. includes power switch­ mile sub-district between Shenandoah has previously been the practice with es and semi-automatic signals at the and Hagerstown, the ruling grade this type of panel. Also the diagram ends of double track at North Ro­ northbound is 1.5 per cent for about includes lamps to repeat occupancy of anoke, Vesuvius and Cold Spring as 0.9 mile between M.P. 99.7 and 100.6. each passing track, as well as each well as at 14 passing tracks. Within This grade includes one 5-deg. curve OS switch detector section and sec­ the limits of the double track there is and one 8-deg. curve. The ruling grade tion of main line opposite each pass­ a power operated crossover at Lofton southward varies from 1.6 to 2.0 per ing track. and another at Pkin. Signaling is pro­ cent for about 0.9 mile between M.P. The switch levers and the signal vided for train movements in either 81.5 and 82.4. The Class Y-6 loco~ levers are equipped with the conven­ direction on both tracks of this section motives are rated to handle 2,750 tons tional arrangements of indication Ju~e, 1944 RA I LWA Y SIGNALING 31 1 lamps. The C.T.C. system includes with common for each direction, thus by a marker lamp on the mast 6 ft. automatic time locking, including style totaling three line wires, these circuits below the center lamp in the operative DT- 10 time-element relays. If a being continued in service. These unit. semi-automatic signal has been wires are No. 10 Copperweld with cleared, and is then "taken away" by weather-proof covering. In numerous Benefits of the Improvements lever control, the switch invol:ved can­ instances the track relays and feeds not be moved until the automatic time were changed end-for-end to get the The benefits of the new improve­ release has functioned, regardless of relay nearer to a C.T .C. field station, ments, including the new section of whether the approach track section is so that the length of line wire to be second track and the centralized traf­ occupied. During the period when added to repeat the track occupancy fic control, can be measured by the the time locking is in effect, all three of the intermediate automatic blocks, average reduction in train time on the indication lamps, on the signal lever would be a minimum. road. The average time for through involved, are extinguished, and as freight trains from yardboard to soon as the locking is released, the Signals at Passing Tracks yardboard, North Roanoke to Shen­ red indication lamp is lighted as in­ andoah in February, 1943, \Vas 7 formation to the dispatcher so that he The automatic signals at the ends hours 18 minutes, which was reduced can save train time bv sendine; out of passing tracks were previously lo­ in February, 1944, to 6 hours 4 min­ new controls for a different line up cated properly for centralized traffic utes, a reduction of 1 hour 14 min­ as soon as such codes would be effec­ control. and, therefore. did not have utes. For southbound trains, between tive in the field. If the dual control to be moved, except at those locations Shenandoah and North Roanoke, the selection lever on a switch machine where the passing tracks were length­ average train time was reduced from is operated from its normal position, ened. An accompanying picture shows 7 hours 54 minutes to 6 hours 5 min­ an indication code is sent to the office the station-enterine; signal at the utes, a saving of 1 hour 49 minutes. which cau o- es both the normal and re- · north end of Buchanan. When in­ On the Hagerstown-Shenandoah verse indication lamps above the cor­ stalling C.T.C., the lower unit was district of 105.7 miles on which C.T.C. responding switch lever to be lighted. added on this signal so that the aspect was installed on only 33.7 miles be­ Each of the two C.T.C. control of a horizontal row of lights over a tween Hagerstown and Bentonville, machines is equipped with a graphic diagonal row could be displayed, with the average reduction in running time train chart. Each morning, this chart the power switch reversed. to direct for northbound trains was 33 min­ is torn off on the line representing a train to enter the passing track. utes, and for southbound trains the midnight, and this graph serves as the This aspect is track-circuit controlled reduction was from 6 hours 4 min­ official record of train movements, on the passing track so that if the utes to 5 hours 4 minutes, a saving the same as the ordinary train sheet passing track is occupied, an aspect of 1 hour. Countine; loaded as well for the sections where the timetable cannot be displayed for a second train as empty cars moved out of and into and train orders are in effect. to enter. Roanoke over the Shenandoah dis­ The panel also includes lamps which Another picture shows the north­ trict, the traffic handled in February, display indications when rock-slide ward station-departure semi-automat­ 1943, was 42,938 cars as compared detector fences are operated, when ic C.T.C. controlled signals at the with 42,117 cars in February, 1944, a-c. power is cut off of certain sec­ north end of Buena Vista. The two which was not much of a total reduc­ tions of the line, or when the air signals are mounted on a bracket mast tion. pressure at an electro-pneumatic located at the right of the main track switch is below a certain minimum. and opposite the fo uling on the pass.: Electro-Pneumatic Power Switches ing track, identically the same as pre­ Signaling Arrangements vious to the change over to C.T.C. Each of the power switches is oper­ The signal applying to the main track, ated by a Type A-20 dual control Prior to the recent C.T.C. program, 112RM, is to the right and has a electro-pneumatic switch machine. the Shenandoah Valley District had higher mast than the signal 112RS When the selector lever is operated, been equipped for many years with which is to the left. and has a shorter the air supply to the switch machine straight a-c. automatic block signaline;, mast and applies for directing trains is cut off, the valve control circuits using position-light signals, and the to depart from the passing track. Ab­ are opened, and an indication code is system included continuously-cori­ solute signals are each so designated sent to the dispatcher's office which trolled three-aspect cab signaling. When changing over to C.T.C., some of the intermediate signals were relocated and the controls were re­ vised, this being made possible by the fact that C.T.C. obviated the neces­ sity for opposing intermediates to provide head-on protection. The neu­ tral a-c. track relays and polar line relays were retained in service. T he absolute permissive block line control circuits include one wire in connection

Dual-control electro­ pneumatic switch ma­ chine on siding switch June, 1944 RAILWAY SIGNALING 312

The second C.T.C. ma­ chine for the control of section from Shen­ andoah to Bentonville

tioned above and is received by car­ rier apparatus at Glasgow, and converted to conventional d-c. codes to be transmitted to the local field sta­ tions between Glasgow and Stuarts Draft. From these field stations, d-e. indication codes are transmitted to Glasgow where they are converted to 14 kilocycle carrier current for transmission to Roanoke. The controls of switches and sig­ nals on the Shenandoah-Bentonville section are sent out from the Roanoke causes both of the indication lamps telephones to the dispatcher. Where a office as coded 18 kilocycle frequency above the switch lever to be lighted. switch with an electric lock is located to Stuarts Draft where they are con- Each selector lever is locked with a within station limits, the lock is con­ -verted to conventional d-e. codes for standard switch padlock in order to trolled by a lever on the C.T.C. ma­ transmission to the various field sta­ prevent unauthorized movement of chine. The electric locks on switches tions in the Shenandoah-Bentonville this lever. The hand-throw lever is, on single track between stations are section. Similarly d-e. indication codes of course, also padlocked. Each controlled automatically by circuits from stations on the Shenandoah­ switch layout is equipped with the on the same line wires that are the Bentonville section are transmitted to standard arrangement of lock rods a.p.b. local line controls, these circuits Stuarts Draft where carrier current and a point detector which is set to being in effect the same as used on apparatus converts these codes to cod­ operate if the switch point is open the various roads including the Chi­ ed carrier of 12 kilocycles for trans­ more than 3/16 in. cago, Burlington & Quincy, as ex­ mission to Roanoke. The compressed air for the oper­ plained on page 203 of the April, At the office and at the field sta­ ation of the switch machines is sup­ 1943, issue of Railway Signaling. The tions, filters are provided to prevent plied by small-capacity motor-driven point of interest is that no extra line interference between the d-e. codes compressor sets. Duplicate compres­ wires are required to control these and the high frequency codes, and, sors, each rated at 3.5 cu. ft. per min., electric locks. of course, there is no interference be­ are located at each single switch or tween the codes at the different high crossover. The compressors are con­ Coded Carrier C.T.C. frequencies. For this reason the con­ trolled automatically, the one in nor­ trols of the three different sections mal operation being set to cut ·in at 55 The two C.T.C. control machines are independent and the line circuit lb. and cut out at 70 lb., while the are in adjacent rooms in the dis­ can be used simultaneously for any auxiliary compressor is set to cut in patchers'· offices at Roanoke. T he con­ two or all three of the sections. at 45 lb. and cut out at 60 lb. Each trols are sent out to the field stations, The advantages of this utilization of the 3.5-cu. ft. compressors is driv­ and the indications are returned by of carrier current equipment may be en by a 220-volt a-c. motor, rated at the means of Union Switch & Signal considered from various viewpoints. ~ hp. Company multiple time code system, On a busy railroad such as this, if multiple application, using only two more than about 50 miles, including Electric Locks on Hand-Throw new line wires between Roanoke and about 30 field stations, are controlled Switch Bentonville. This project includes as a unit, there ~ will be so many con­ three separate arrangements of time trol and indication codes that there At various places, as shown on the code sending and receiving equipment, may be too much time delay for in­ diagram, house tracks or spurs lead­ each with a capacity to handle a max­ coming indication codes. When meets ing to industries are connected to the imum of 35 stations. A point of spe­ and passes are being made on close main line with hand-throw switches. cial interest is that the system as a timing, a few seconds may avoid stop­ At each of these locations, the pre­ whole requires only two line wires ping a train. vious switch stand was replaced with throughout the Roanoke-Bentonville If the carrier current system had a T -21 hand-throw switch-and-lock territory. not been available, and if the controls movement including an electric lock The controls and indications for were to have been separate for the which locks the operating lever in the 44-mile section between North three sections, one of several choices the normal position. These layouts Roanoke and Glasgow are effected by would have been available. There include lock and point-detector rods conventional d-e. codes on the two could have been three control ma­ which lock the switches in the normal line wires and similarly d-e. indication chines, as for example, one at Ro­ position. In each instance, a Hayes codes are transmitted on the same two anoke, one at Glasgow and a third derail, located at the clearance point line wires from the field stations in at Shenandoah. Or, with the ma­ on the turnout, is pipe connected to, this section to the office at Roanoke. chines as they are in Roanoke, with and operated by, the T -21 hand-throw The controls for the switches and separate line circuits there would have switch and lock movement. signals between Glasgow and Stuarts been two additional wires from Stu­ A telephone is located near each Draft, 42 miles, are coded 20 kilo­ arts Draft to Roanoke, 86 miles, and switch. When one of these switches cycle frequency which is transmitted two additional wires from Glasgow is to be used by a train, the conductor over the same two line wires men- to Roanoke, 44 miles. Roughly the June, 1944 RAILWAY SIGNALING 313 use of the carrier system saved about of the TC relay which in turn is en­ each case is enclosed with a glass door. 260 miles of copper wire, or about ergized through contacts of the trans­ These sets are identical and inter­ 108,940 lb. mitter relay T . When a carrier code changeable with the exception that cycle is to be sent out, the T relay is plug-connected coils can be changed to Features of the Line Circuit energized for each impulse, which adapt the apparatus for operation on picks up TC, thus allowing an im­ different frequencies mentioned pre­ A particular feature of the line cir­ p).llse of 20,000-cycle energy to feed viously. (See Fig. 1 page 314 next.) cuit on this installation is that it is over the pair of wires to the field sta.­ The' oscillator-amnlifier unit oper­ arranged to accommodate a Type-H tion at Glasgow, at which point this ates from any 110-volt, 60-cycle carrier telephone system on the same energy is picked up by a receiving source, and this source comes into the wires with the C.T.C system includ­ filter and is amplified to operate a unit through plug connectors BX110 ing its carrier frequencies and the C relay which is released at the end and CXllO. This source is connected p~ysical telephone circuit which is of the impulse. T hus the C relay at to the primary of a power trans­ used mainly for maintenance purpos­ Glasgow follows the code impulses former, and the unit takes about 40 es. The Type-H carrier telephone sent out by the TC relay at Roanoke. watts. The power transformer has circuit has one terminal at Roanoke The pair of line wires from Ro­ three secondaries. The secondary and the other at Shenandoah from anoke end at Glasgow, there being no supplies the heater voltage for the ·which point it connects to a dispatch­ physical connection between these 6C6 oscillator tube, the 42 ampli fving er's circuit for the territory between wires and the pair that extends on tube for the oscillator, and the 2050 Shenandoah and Hagerstown. The north from Glasgow to Stuarts Draft. tube which is a hot cathode gas dis­ line circuit is carried through a West­ Operation of the C relay at Glas­ charge type of tube. The SV4G tube ern Union cable for a little more than gow causes conventional d-e. code im­ is a standard type rectifier having one mile from the office at Roanoke. pulses to be fed out on the pair of line two plates for full-wave rectification. Suitable matching is provided for wires north from that point to select The high-voltage secondary winding voice and carrier frequencies at the stations and switches or signals in the has the outside ends connected to the junction between the cable and open conventional manner. plafes 4 and 6 of the rectifier, and wire line. When an indication code is to be the center tap grounded. The heater There is a coded carrier repeater lo­ sent in from one of the field stations or cathode of the tube is positive with cated at Glasgow which is normally between Stuarts Draft and Glasgow, respect to ground, which is minus d-e. inactive and may be brought in service the apparatus at the said field station The rectified current is passed at any time by the dispatcher sending shunts the line circuit to increase and through a filter choke, and on the a special code to the location. The remove the shunt to decrease the line other side of the choke there is a coded carrier repeater is brought into current in the conventional manner. condenser connected to ground. This service automatically in response to an This increase and decrease operates choke and conAenser take the ripple open wire between Roanoke and an impulse relay RL at Glasgow. out of the rectified d-e., and the re­ Glasgow by making use 6£ the field RLP is a repeater of RL. A 14,000- sult is steady d-e. for supplying plate station disconnect arrangement. cycle oscillator at Glasgow is normally voltage to the oscillator.- Because of the length and high re­ suppressed by a normal contact of The 6C6 oscillator tube has the sistance of the wire in the Stuarts RLP. However, when· RLP is re­ primary of the oscillator coil connect­ Draft to Bentonville section of the versed in response to an increase in ed in the plate circuit to No. 2 pin. line circuit, most of which is No. 10 line current, the 14,000-cycle energy A resistor connects + to the No. 3 Copperweld 40 per cent conductivity, is sent over the pair of line wires di­ grid. Grid No. 4 is tied to cathode No. it was desirable to use the P-4 type rectly to Roanoke, where this energy 5, and these are connected to ground impulse relay. The main reason for is picked up by the office receiver filter through a resistor. There is a feed­ this was to economize in the size of and amplified to operate the OC relay. back from the secondary of the oscil­ line battery. This explains why a This delivers a pulse through the re­ lator coil through a resistor to the grid repeater of the impulse relay was sistor and condenser to the upper located on the cap of the tube. It is used at Stuarts Draft. There was not winding of the office OR relay which the inductance of the oscillator coil the same requirement existing at is reversed. Thus the OR relay, in and the capacity of the associated con­ Glasgow but a similar circuit was in­ the office, follows the RLP relay at denser that determines the frequency stalled in the interest of uniformity. Glasgow, and the OR office relay at which the tube will oscillate. causes indications to be displayed on Details of the Carrier System the control machine in the usual man­ Operatlon of the Tubes ner. At the Roanoke office there are Thus, insofar as the C.T.C. control The No. 4 grid of the 42 tube is three separate line coding units. The machine is concerned, the operations driven by frequency generated in the one for the Roanoke-Glasgow section are similar for both the ordinary d-e. 6C6 tube. This grid can be driven is connected to the line in the usual line code section and the carrier sec­ as hard as desired by the adjustment manner. The two line coding unit5 tion. of the potentiometer. When there is for the Glasgow-Stuarts Draft and no grid potential, there is no change the Shenandoah-Bentonville sections Assembly of Carrier Equipment in the plate current which may be are each connected to the line through traced from plus d-e. through the the coded carrier apparatus. In order The basic elements of each set of primary winding of the occi llator out­ to simplify the statements, the fol­ coded carrier equipment, including the put transformer, plate pin No. 2 on lowing discussion will be confined to oscillator and amplifier tubes, are the 42 tube, through the 42 tube to the carrier for the Glasgow-Stuarts mounted and wired in a standard cathode No. 5, thence to ground Draft section. sized sheet metal case. The panel of through a resistor. \Vhen the po­ At the office there is an osrillator each set is equipped with scales and tentiometer is mrwed ~o there is a which is capable of delivering 20,000 knobs for operating potentiometers large voltage on No. 4 grid, the plate cycle energy by means of an el e ~tro nic for adjusting the voltage of out'2:oing current changes by a lart;e amount tube. The 20,000-cycle energy is nor­ codes and for adjusting the amplifica­ at the frequency of the oscillator, and mally suppressed by a reverse contact tion of incoming codes. The front of this makes a large carrier current in 314 RAILWAY SIGNALING June, 1944 the primary of the oscillator output down the tube between grid No. 5 and taken from the rectifier before it transformer. T he secondary of this cathode No. 8 comes from the receiv­ passes through the filter choke, and transformer is matched in impedance ing filter. One coil lead of the receiv­ passed through the limiting resisto r, to the line circuit, and goes to the ing filter is connected to the receiving the winding of C relay which is con­ oscillator terminals on the unit. potentiometer (amplifier gain), and nected to + R and - R terminals T he 2050 tube may be called the the other coil lead is connected to the of the unit, through the tube from relay tube, because it is the one which tube gt·id. Voltage across the receiv- No. 3 to No. 8, and back to minus through the potentiometer. As point­ ed out before, current for operating this relay is rectified a-c. and its volt­ Bof+om vie w of top plafe age drops to zero every one hundred and twentieth of a second. A con­ denser is, therefore, placed across the Rec. fil+e~ ex 110 Line • • terminals of the relay ( + R and - R) to keep C from chattering. ax 110 Line It is characteristic of a gas tube that once it becomes conducting from plate, or more properly anode, to cathode, it will continue to conduct even though voltage is removed from the grid or trigger circuit. By using rectified a-c. to operate the relay, the tube becomes non-conducting every half cycle if the grid is not energized by carrier frequency. This allows C to drop out if the incoming signal is off, and causes it to pick up on the next half cycle if the incoming sig­ nal is on. If the bias control of the amplifier is turned up to about 6, there is suf­ ficient voltage on No. 5 grid to trig­ ger the tube with no incoming signal. The most sensitive adjustment is back from this point just where the relay drops out. However, this· is more sensitive than the unit may operate because pole changing the line and other noises all contain a slight amount of high frequency, and the C relay would possibly not operate properly unless the amplifier gain were moved back a small fraction of a division. 3 The transmitter filter, which is plug connected, is applied at the left por­ Ccrp. tion of the top of the standard oscil­ 11 0 v. lator-amplifier set. This filter passes 60~ the frequency for which it is tuned and is high in impedance to every frequency except the one to which it is tuned. A plug-connected receiv­ ing filter is applied at the right por­ tion of the top of the standard oscil­ lator-amplifier set. A receiving filter is of the same general construction Fig. 1-Schematic diagram of circuits for an oscillator-amplifier as a transmitting filter except it con­ tains two sections instead of one in picks up the C or OC relay in re­ ing filter terminals is applied to the the transmitting filter. These filters sponse to incoming frequency. The tube, since one side is connected are tuned and sealed by the manufac­ 2050 is a hot cathode gas discharge through a resistor to grid No. 5, and turer. type of tube, and cathode No. 8 is the other side is connected to cathode The relays used in connection with heated by a heater on pins No. 2 and No. 8 through part of the potentiom­ the coded carrier are the plug-con­ No. 7. The tube normally presents eter. If an initial bias voltage is put nected Type-KP, and are mounted on an insulated circuit between plate 3 on grid No. 5, it will take less in­ top of the oscillator-amplifier set. and cathode 8. However, when the coming signal to trigger the tube. This Two such relays are required on each tube is "broken down" by applying initial grid bias is adjusted by the set at Roanoke and two on each set at a small voltage between grid No. 5 potentiometer, due to current through Glasgow and at Stuarts Draft. and cathode No. 8, the tube becomes it and a series resistor, and this ad­ In case of a failure of any part of conducting between plate No. 3 and justs the sensitivity of the amplifier. one of these sets, a standby set can cathode No. 8. Current for operating C (Style­ be cut into service quickly. At the The triggering circuit for breaking KP biased polar relay) normal .is office, the code carrier set which is June, 1944 RAILWAY SIGNALING 315 in operation is connected to the line when it arrives at Glasgow. This volt­ time it is picked up. This relay repeats through back contacts of an eight­ age range complies with those of car­ the operation of T in the office cod­ point change-over relay, and the rier current systems used for tele­ ing unit, and is energized from B16, standby set can be placed in operation graph and telephone. terminal 24, front contact T -C3, back and connected to the line through the front contacts of this relay. If a failure occurs, the dispatcher can cut Terminal Symbols used with Carrier Circuits in the standby set by throwing a tog­ 0 Terminal on office line coding uni+ gle switch on his desk which com­ To Remo+e pletes the circuit to energize the @ Terminal on C. T. C. cabine+ferminal board s fcdion change-over relay. At Glasgow, for E!1 Terminal on carrier KP relay plug connector example, there is a change-over relay 0 Terminal on auxiliary line T C associated with each oscillator-ampli­ fier unit, which can be energized se­ held sfa-fion lectively by throwing a toggle switch 83 • disconnec+ bu+fon on the control panel and pushing a ~816 button to send out a control code. Once each week, the standby sets are cut into service as a test.

55 Carrier Circuits in the Office .

The Fig. 1, shows a schematic dia­ gram of the circuits for a typical 53 oscillator-amplifier unit of the coded 56 carrier system. The 60-cycle energy • 56 feeds from commercial lines, which • /7 have several independent sources so .------o/7 that complete failure is practically un­ known. If these sources all fail, how­ ver, the set can be fed from a tuned alternator which is fed from the local office storage battery, the change-over being automatic. Incidentally, this tuned alternator is the ~ame unit which feeds the synchronous motor for op-erating the graphic train chart in the C.T.C. control machine in case of an a-c. power outage. This circuit will function properly with approximately 6 volts coded on the line at Roanoke, this being re­ duced by line losses to about 2 volts

Office Line Coding Unit 816)~ t ~ tnaf~afing { ~ )N l1q hfs ~~E&1:-:-0 -----3-+~ Office Carrier Equipment

Fig. 2-Circuits in the office for the coded carrier control

At Glasgow, the feed for the oscil­ contact of P C, terminals 55 and 83 lator-amplifier set is taken from to the winding of the T C relay. Open­ transformers fed from the signal ing and closing T codes the relay TC power distribution line. If this source which in turn codes the carrier out­ fails, a power-off relay cuts in a bat­ put. tery feed for a tuned alternator which The OC relay at the office is the feeds the required 110-volt 60 cycles one that is connected to the amplifier to the oscillator-amplifier. and it responds to 14,000-cycle car­ rier frequency impulses sent in by Office Circuit for Carrier the field . This relay is normally de­ energized, and operates no rmal only The Fig: 2 shows the circuits in when a 14,000-cycle carrier impulse the office for the coded carrier con­ is received by the amplifier. W hen Rock slide detector fence alongside a trol. The TC relay is so named be­ operated normal, this relay causes re­ hand-throw switch stand cause it transmits a carrier pulse each lay OR to move to its reverse posi~ 316 RA I LWAY SIGNALING June, 1944 cion. The circuit is from B16 through at the remote station in the same man­ the winding of relay TC. This cir­ a resistor, contact lN of relay OC, ner as 16 at the office drops PC at cuit is closed during the release time condenser, back contact TC5 to the the beginning of the l~st step of the of relay PC. upper coil of relay OR. It is now code. This is accomplished by send- Release of the PC Relay

At the end of an indication code From office To Field s+a+ions when 16 drops the PC relay, relay TC picks up momentarily to send a pulse of 20,000-cycle energy. The length of this 20,000-cycle pulse is, by de­ sign, of sufficient duration to insure the release· of PC at the field carrier location (Glasgow). For control codes, TC follows the code, and for indication codes OC fol­ lows the code. Contacts of these re­ lays (lN of TC and 3N of O C) operate indication lamps. If for any reason the office should fail to follow so the LBP would release to drop the pole changer, the pole change re­ lay at the field is dropped out due to the office sending an impulse of 20,000-cycle frequency from the time PC releases until PCP releases. In this manner the office can make a fiel d station repeat a code.

Carrier Circuits at Glasgow

T he circuits at Glasgow are shown in Fig. 3. Battery for the remote line is located at Glasgow, also the limit­ ing resistance, impulse transformer, impulse relay RL and its repeater RLP pole change relay PC and the pole change repeater PCP, normal repeater of RLP, NSA; repeater of NSA and PCP, NPCP; and a re­ peater of NPCP, NPCPP. The impulse and carrier responsive relays are Style-KP plug-in relays located on top of the No. oscillator­ 12 12 1 II C amplifier unit. The pole changer and 816 ~ -­ pole change repeater relays are ~ \ Style-L relays similar to correspond­ ing relays in the office coding unit, II RLP B/6>-f&------.-----. R PC and they are housed in a sheet metal 7 case with plug-in top plate. This ~ 2R unit is known as the auxiliary line unit. · The remote line is equipped with 20 filters, so that the line circuit is used N/6 also for telephone communication. A voice and Type-R carrier pass fi lter connects the two lines. Battery is fed out on the line north from Glasgow exactly the same as if the office were located at that point, Fig. 3-Coded carrier circuits at Glasgow and the carrier responsive relay C opens and closes the battery just the apparent that OR will follow the ing one impulse of 18,000-cycle con­ same as if it were the office trans­ same code as O C. On the first step trol frequency on the 16th step of an mitter. This C relay is connected to of an indication code, OR reverses to indication code. the amplifier, and it is picked up pick up PC in the usual manner. whenever there is 20,000-cycle energy As will be pointed out later, there Feed for the TC Relay on the line. Since the relay C is noth­ is a PC relay at the remote line loca­ ing more than a carrier repeater of T tion which remains up during an in­ T he TC relay receives energy for at the office, it is apparent that con­ dication code the same as the PC re­ picking it up momentarily from B-1 6, trol codes are sent by opening and lay at the office. Some provision must front contacts PC-C6, front contact closing the battery in accordance with be made for opening the PC relay 16-A5, terminals 70, 55, and 83 to the code, the same as if the office June, 1944 RAILWAY SIGNALING 317 removed so 14,000-cycle energy goes controlled section to be returned to out on the line to pick up the OC normal even though no reset pulse relay at the office. The OC relay de­ would be transmitted from the office. livers a pulse in the office to reverse T his is accomplished as shown in Fig. OR. It is thus apparent that each 3. During an indication code, relays time RLP is reversed in response to PCP and NSA receive energy over an increase in current, the OR relay the contacts of relay RLP, PCP being in the offic e is made to reverse through energized over the 2R contact and the medium of OC carrier relay. Also NSA over the 1N contact. Relay each time RLP goes normal in re­ NPCP is controlled over front con­ sponse to a decrease in current, the tacts of relays PCP and NSA in OC relay delivers a pulse to position series. The slow action of these re­ relay OR normal. In this manner OR lays is selected so that relay NPCP is made to follow RLP for a complete will not release during any indication. indication code, after which the of­ code. fice sends out one impulse of 20,000- It will be evident that in the cycle energy to normal C and drop event of no code being on the line PC. and relay RLP stationary, either PCP There is no M relay at the Glasgow or NSA will release. Either of these location to shunt the impulse trans­ relays releasing will release relay former during a control code. Each NPCP. Note that the stick circuit time the C relay opens and clcses the of relay PC is carried over a front line, there is a decrease and increase contact of relay NPCP and the pick­ in line current which applies voltage up circuit of PC is carried over a to the top coil of RL. During a con­ front contact of relay NSA. Relay trol code, it is necessary that RL stay PC will, therefo re, become de-ener­ normal so that RLP and PC do not gized in response to relay RLP be­ pick up falsely. On the first step of a coming stationary for a period some­ control code, when c operates normal, what greater than the length of the the current decreases and RL is giv­ longest pulse of a normal code. en an impulse to position it normal. Relay NPCPP is a repeater of re­ As it is already in the normal position, lay NPCP. The contacts of this re­ this impulse does no harm. However, lay are used in the disagreement cir­ when C reverses to close the line, the Automatic switching panel for the 4,400- cuits for the shunting of the sec­ volt a-c. signal power pne at impulse is in the direction to reverse ondary of the impulse transformer in the Bueno Vista sub-station RL, and this reversal is prevented by response to changes in the position of PCP which is picked up each time C relay PC and for the disagreement transmitter were located at Glasgow. When a field station on the Glas­ gow-Stuarts Draft section starts to indicate, it shunts the line in the reg­ ular manner to ask fo r a pole change. This shunt increases the current in the impulse transformer, and re­ verses the impulse relay to pick up relay RLP which picks up the pole changer relay. The pole changer re­ The coded carrier lay both picks up and sticks over a equipment in the reverse or de-energized contact on case at Glasgow C, and for this reason an impulse of control frequency can break the pole changer any time during an indication code. To prevent a false kick on RL when PC picks up, a PCP relay is provided to repeat PC. As soon as PC picks up, the secondary winding of the im­ pulse transformer is short circuited by front contacts PC-B-1 and back comes up on a control code. The cir­ circuits which energize the lower contact NPCP-A4. This shunt re­ cuit for holding RL normal is from winding of the RL relay under this mains on until NPCP picks up. Also, B-16, to left through lower coil of same condition. RL is guaranteed to be in its reverse RL, terminal 15, front contact PCP­ position by a local circuit from B16, A3 to NPCPP-A3 and back contact Construction of the Project through part of lower coil of RL, PC-C1 through terminals 3 and 20 to back contacts of NPCP and NPCPP N-16. T his signaling project was planned to N-16 over a front contact C1 of and installed by the signal forces of relay PC. This circuit is also broken A New Feature the Norfolk & W estern, under the di­ when NPCP picks up. rection of J. A. Beoddy, superin­ Relay RLP normally suppresses The relay circuits within the auxil ­ tendent telegraph and signals. The the 14,000-cycle oscillator. When iary line units at Glasgow and Stuarts major items of equipment were fur­ RLP is reversed in response to an in­ Draft have a new feature which per­ nished by the U nion Switch & Sig­ crease in current, the suppression is mits the d-e. polarity of the carrier nal Company.