C.N. Montréal terminal has new type of interlocking

A total of 57 switches, 64 crossovers and 197 signals, on 9 road miles throughout 11 zones, are controlled from one central machine using a new form of code control

Concurrently with the development and construction of its Central station in Montréal, Que., the Canadian National made numerous track changes and additions throughout nine road miles and, as a part of this project, new interlocking facilities, including electric switch machines and searchlight signals, were installed throughout, a special feature being the central control of these facilities from one machine which is of a new and novel design.

When the Canadian National Railways were formed in 1922 by the amalgamation of several railroads, two of these railroads had passenger stations in different sections of Montréal. The Bonaventure station, in the southern section of the city, served trains to and from points west and southeast. The Tunnel station, located centrally in the business section of the city at the south end of a three-mile double-track tunnel under Mount Royal, was used by trains to and from the north.

The Canadian National Railways Central station, which was placed in service on July 14, 1943, was constructed on the same property as the old Tunnel station, trains to and from the north using the tunnel as previously. In order that the trains which previously used the Bonaventure station could use the new Central station, a new section of railroad about three miles long was built 'south from the site of the new station to a wye, with one leg connecting with the east-and-west main lines at a point just west of the Victoria bridge, and the other leg connecting with the main line near Point St. Charles station. All of this new line is elevated above street level, and crosses the Lachine canal on a new double-track lift bridge. As a necessary part of the project, a new coach yard was constructed near the Point St. Charles shops. A new double-track connection to this yard extends across the old east-and-west main line just west of the west end of the Victoria bridge.

Electrical operation of trains was previously in service through the Mount Royal tunnel, and this same form of electrical propulsion was installed on the new connection from the Central station to the east-and-west line, including the passenger tracks between the Victoria bridge on the east and Turcot yard on the west. All train movements into and out of the new station are made with electric locomotives. Track layouts for changing from steam to electric locomotives and vice-versa are located at Turcot yard and at a point just west of Victoria bridge. The distance from Victoria bridge to the Central station is 2.3 miles, and from Turcot yard to the new station is 4.7 miles.

The interlocking includes 9 road miles, involving 28 track miles, and is divided into 11 zones.

A daily average of about 140 passenger train movements are made into and out of the Central station, including equipment trains to and from the passenger coach yard and multiple sections of certain trains, and about 95 freight trains which, although not using the Central Station, comprise a major part of the traffic through the interlocker. Besides these, there are numerous movements connected with the changing of engines on inward and outward passenger trains, many light engine movements and the passenger and freight switching involving the main and station tracks.

Freight trains from the east and southeast enter Montréal via the Victoria bridge and then move to the Turcot yard. These trains may be routed via the old double-track main line by way of Point St. Charles station, or over a new line, known as the Butler diversion, which is located south of the new coach yard to avoid interference between freight trains and coach trains moving between the new coach yard and the new Central station. All these freight train movements, as well as hundreds of switching movements throughout the entire area, are made by signal indication under interlocking protection. An average of at least 800 train and switching movements are made daily in this interlocking area.

Two-Unit Low Signals

A total of nine road miles of lines are included in the interlocking area. The number of main tracks varies from two to six, as shown in the diagram, so that a total of 28 track miles are included in the interlocking. Each track is signaled for train movements in either direction.

Throughout the entire terminal project, the new interlocking signals are the two-unit low type, this type permitting such signals to be located as required to utilize all the length of track available. Each signal comprises two searchlight signal units, each capable of displaying req., yellow or green. Green-over-red is the "Clear" aspect, which indicates Proceed. Yellow-over-red is the "Approach" aspect, which indicates "proceed prepared to stop at next signal". Red-over-yellow is the "Restricting" aspect, which indicates "proceed at restricted speed". This is the call-on aspect, displayed when one or more of the track circuits is occupied. Red-over-red is the "Stop" aspect. Electric switch machines, rated at 110 volts d.c., are used at the interlocked switches. Main-line handthrow switches are equipped with electric locks which are controlled from the interlocking machine.

Two unit signals display four aspects.

The switches are operated by 110-volt machines

New Type of Interlocking Machine

The control machine for this entire interlocking is located in a tower on the west side of the track just north of the new lift bridge over the Lachine canal. The controls are of the all-relay type; i.e., the locking is accomplished by interconnections of circuits, so that there is no mechanical locking between levers and no electric lever locks.

The interlocking machine is different from any used previously. The levers and accompanying indication lamps are inserted in a steel panel 44 in. high which is mounted at an angle of 30 deg. The lower edge of the panel is 30 in. above the floor, so that the levers on the panel are all easily reached by a man standing at the machine. The total length of the machine panel is 12 ft. 6 in., the end. sections being set at an angle.

The levers are of the miniature type and of a special design, as shown in a close-up view in one of the accompanying illustrations. The part of the lever which a leverman grasps between the thumb and forefinger is about 1/2 in. high and 1 in. long. In order to operate a lever, it must be pushed down about 1/8 in. against spring pressure, thus releasing a catch, after which the lever can be rotated on a vertical shaft through the face of the panel. A switch lever can be rotated 90 deg. from the normal to the reverse position or vice versa. A signal lever normally stands on center and can be rotated 45 deg. to the right or to the left to control corresponding signals. In order to control a signal to display the call-on, Restricting aspect, red-over-yellow, the signal lever must be positioned and a button on the panel below the lever must also be depressed. When a signal lever is moved to an R or an L position, a steady white light appears above the lever, and this light continues to burn until the signal clears and an indication to that effect is transmitted to the control machine, at which time the lamp above the signal lever is extinguished, and a lamp is lighted in the symbol representing that signal on the illuminated track diagram.

The hand-throw main-line switches within the entire interlocking territory are equipped with electric locks, which are controlled by levers in the interlocking machine. The lamp above each electric lock lever is normally extinguished. When the lever is reversed, a steady-burning light appears above the lever if circumstances in the field are such that the lock can be released. These conditions are that the lever-controlled signals governing the switch must be at stop, their associated approach locking relays must be energized, and the track sections in the route which include the switch must not be occupied by a train moving toward the lock, except that after the track section in which the switch lock is located has been occupied for a pre-determined time, a release may be obtained automatically to permit the switch to be unlocked.

The train-starting control panel is on a desk in front of the new machine, with the track model to the rear.

Illuminated Track Diagram

The illuminated track diagram is 4 ft. 6 in., high and 34 ft. in. long, and is mounted on pipe posts to bring the bottom of the model 5 ft. 9 in., above floor level and 3 ft. 10 in., to the rear of the interlocking control machine. At this location the track diagram as well as the indication lamps, are plainly visible to the men operating the machine. From the photographs shown herewith, it will be noted that one half the track diagram is on the upper half of the model board, and the other half is on the lower half. In a corresponding manner, the levers in each half of the panel of the interlocking machine correspond with the tracks on that half of the track model.

The diagram is provided with lamps to indicate track occupancy, which lamps are lighted when a train occupies the corresponding track section. As mentioned previously, when a signal clears, a lamp on the model board is lighted in the symbol representing that signal. Likewise, when an electric lock on a hand-throw switch is released, a lamp on the model board is lighted near the symbol representing the electric lock on the corresponding track switch.

Interlocking Divided into Eleven Zones

So far as the men in charge of the control machine are concerned, the interlocking on the entire 9 road miles is controlled as one large interlocker. From a signal engineering and construction standpoint, however, the interlocking is divided into eleven zones. At a central point in each zone, there is a concrete house known officially as a bungalow. Conventional direct-wire control circuits extend from each bungalow to the switch machines, signals and track circuit connections in that zone, the same as if there were a conventional type interlocking control machine in the bungalow. The novel feature of this extensive interlocking is that the entire eleven zones are controlled from one machine, which, as stated previously, is located in a tower near the new lift bridge.

The control of so many switches, signals and electric locks over such an extensive area would, of course, require too many wires if conventional direct wire circuits were used. On the other hand, line code control, as ordinarily used in centralized traffic control, would not be entirely practicable for application to the control of such a large number of switches and signals. For these reasons the Type-S Form 508 polar code control system was applied.

In this system of interlocking, controls are transmitted from the control machine to each bungalow on three wires, and indications are transmitted from each bungalow to the control machine on three other wires, the two three-wire arrangements being entirely independent so that controls to, and indications from, a bungalow can be transmitted simultaneously.

Train-Starting System

The new signaling includes a train-starting indicator system by means of which the gateman in the passenger station, the train conductor on the platform, and the train director in the control tower, inform each other concerning the loading of a train before departure.

The train-starting system control panel is on the train director's desk, in front of the interlocking machine in the tower. On this panel, there are, in a vertical row from top to bottom, three indication lamps and two control push buttons for each station track. On each train platform in the station are a platform-indication signal and a key switch. At each gate on the station level are a yellow lamp indicator and a push button.

When a train on a given track is ready to load passengers, the conductor operates a key circuit controller on the platform for the direction the train is to move. This causes a red light to be established on the proper signal on the platform and also causes a control to be transmitted to the tower to light the red (ready to load) lamp on the station-starting control panel. When the towerman operates the acknowledgment button for that track, the red lamps on the station platform signal and on the towerman's cabinet are extinguished and yellow lamps are lighted at both of the locations and at the gateman's indicator. The yellow light directs the gateman to open the gate.

Small section of the new interlocking machine.

As the time approaches for the train to depart, the gateman closes the gate and allows time for passengers to descend the stairs and board the train. Then he presses his push-button, which extinguishes the yellow lamps on the gateman's indicator, on the platform indicator, and on the train director's desk, after which the green lamps on the platform indicator and on the train director's desk are lighted. The towerman then lines the route for the train and clears the signal to depart. The controls between the tower and station for this train-starting indicator system are accomplished by polar code similar to that already referred to.

This interlocking system was planned and installed under the jurisdiction of R. G. Gage, chief electrical engineer of the Canadian National, and under the direction of J. J. Ginty, superintendent signals. The plans and principal items of the interlocking equipment were furnished by the Union Switch & Signal Company.