RESIGNALLING OF ST. ENOCH STATION,
GLASGOW.

NEW EQUIPMENT.
Where power working is adopted for points and signals no limit as to distance from the point of operation is now imposed by the Ministry of Transport, provided certain appliances with the requisite safeguarding controls are included. It has therefore been possible at St. Enoch to greatly extend the section controlled from the new box. and the sections are now as below, three in place of seven :

St. John's to St. Enoch.
St. Enoch to Gorbals Station,
St. Enoch to Port Eglinton.

These figures do not include 10 levers used in ground frames at the platform buffer ends.

Although the levers have been reduced in number the lever movements will not, of course, be reduced in the same proportion, as the same number of signals remain to be operated - approximately so at least - as before, only the dual controls being reduced in number and the route levers entirely dispensed with.

As the signalman in the new box will only be able to see a small proportion of the area he controls and the appliances he operates, he must be provided with apparatus to take the place of his loss of vision and all that goes with such loss.

To describe the functions of the various parts which go to make up the whole machine I shall use the analogy of a living organism: the signalman must therefore have :-

(a) Nerves . (Train describers).
These take the place of the block instruments and advise the signalman that a train awaits entry into his section.

(b) Eyes. (Track circuits).
To give the signalman visual repeat- indication of the presence, and situation of a train or trains in his section.

(c) Arms or Members. (Point motors and Electric Signal Lights}.
To handle the train on its predetermined route.

(d) A Brain. (Signal Frame).
To correlate the messages received from nerves and eyes and so move the arms or members to control the movements of trains.

The items enumerated are as follows:-

(a) NERVES, TRAIN DESCRIBERS.
This apparatus being somewhat extensive in its ramifications can only be described in brief outline.

Owing to the increased area or section under control from St. Enoch new box, when handling passenger traffic, the signalman will have at one and the same time, three successive trains running concurrently on the same lines of rails. Obviously under these conditions ordinary block working is out of the question, therefore, train describers take the place of the block instruments.

The describers consist of transmitting and receiving panels with the originating points of transmission in the Up direction at St. Johns and St. Enoch, and in the Down direction at Strathbungo Junction on the G.B. & K. Line, Bellahouston No. 1 on the Canal Line and Pollock Junction on the Main Line. In the Down direction, cabins situated intermediately between the originating transmission point and the receiving box re-transmit all train indications received. Early indication is therefore given to St. Enoch of all approaching traffic.

The receiving panels give an illuminated indication showing both description and origin of each train and also its position in the section "queue," i.e., whether first, second or third. The first train indication vanishes when the train reaches the clearing track circuit in the station area, the second train indication then takes the place of the first- train indication, the third train indication, the place of the second train indication and a fourth train can now he indicated forward in place of the previous third train. This alteration to the indicators is entirely automatic in action being operated by the passage of the trains over the various track circuits utilised to mark the clearing points. The St. Enoch receiving indications (down line trains) are further classified as "In Section" until such time as the Home Signals protecting Gorbals Junction points have been passed in the clear position and the necessary track circuit occupied ahead when the indications change over to the ''Arrival' column of the panel.

Push buttons are used for all transmission purposes and re-setting keys, cancellation keys and emergency transmit keys are provided to cover all classes of failure and altered transmission required for the expeditious working of traffic.

St. Enoch is also provided with an indicator which shows all transmitted train indications for the Up Lines so long as the trains concerned are under control of St. Enoch signals. Incorporated with this panel is a platform "ready to depart" indicator with illuminated stencilled figure indications, 1 to 12 ; this indicates when a train is ready to start and will be operated by the platform staff.

A special instrument is provided in St. John's to cover setting back, shunt forward and other permissive workings on the Saltmarket Lines.

(b) EYES. TRACK CIRCUITS.
A track circuit is a means whereby a portion or portions of the two running rails is insulated from the neighbouring lengths, then supplied with electrical energy—in this case 3 Volts A.C.—and becomes a constantly energised electrical circuit. Controlled by these electric circuits are locks on certain signals and point levers only energised (i.e. free) when the full voltage is available. If the two rails forming these circuits are connected as by a pair of wheels with their connecting axle a "shunting" effect is obtained and this allows the current to follow the line of least resistance via the wheels and axles instead of flowing through its normal circuit to free the electric lock or locks on the levers controlled i.e. whilst the current is being "shunted'' the levers controlled become locked.

We are therefore able, by means of' these track circuits to exercise control over the levers of the signal frame (or brain) and so prevent illegitimate use being made of the points or signals (arms or members).

Actually, of course, there is interposed between the wires from the track circuited portions of the rails and the lever locks instruments called relays. These are a form of circuit maker or breaker as the case may be amd their types and functions can he summarised as hereunder :—

TRACK LINE AND CABIN RELAYS. Used as wire economizers.

"STICK" RELAYS Used in connection with the sectional release route locking, changing of light signal indications to red through occupancy of the track circuit ahead, etc., etc.

TIME ELEMENT RELAYS Used to operate locks on signal and point levers for a limited period of time maximum 1 minute - once a specified track circuit has been occupied by the leading vehicle;

In all 160 separate track circuits are provided in the new St.Enoch area, these indicate fouling points, trains standing at signals, etc. They are also used in connection with (ho locking of signal and point levers, sectional release route locking. i.e. holding the route ahead with point levers in normal or reverse position—once the signal has been passed with its operating lever over: approach controls (to prevent a signal clearing until the leading vehicle is close to same, i.e. carrying out rules 10 and 13b): putting signals to danger after a train has passed : selecting calling-on indications and providing clearing points for cancelling train describer indications.

In addition. the track circuits usually provide the signalman with eyes in the form of an illuminated diagram of the lines which repeals the condition of the 160 track circuits. Track circuit clear-- no light shows on diagram : track circuit occupied—two red lights show for each track circuit occupied.

Embodied in this diagram is a train waiting indicator for Down Line trains standing at No. 200 signal (also Gorbals Station Down Home). This indicator is operated by the Signalman in Gorbals Station box and takes the place of a track circuit at that signal.*

It is by means of track circuiting that we are enabled to arrange the distance apart we can run and store trains on the same line of rails, this being done by the use of overlaps and overruns. The word overlap is used to describe a length of separately track circuited line, marking a given distance ahead of a signal the forward termination of which marks cessation of control on a rear signal or signals. Should this distance be marked by a track circuit extended from the rear of and past the signal, the arrangement is then called an overrun.

In this scheme there are both overlaps and overruns full-filling the same purpose and so arranged that we can. with the leading train at a standstill at a signal, ''close-up" successive trains to a minimum distance of 70 yards apart between head and tail. The minimum distance of these same trains whilst running concurrently must, of course, be a minimum distance apart of two signals plus the 70 yards overlap.

Where calling-on signals are provided, trains can be stored, buffer to buffer, but their closest concurrent running is subject to the conditions above described.

(c) ARMS OR MEMBERS.
POINTS
All points will be operated electrically by a 1/3rd H.P. 110 Volt D.C. Motor each motor being a self contained unit, complete with electric detector, proving the two switch blades and the facing bolt in the "in'' position. All point motor point slides are fitted with an electrically operated lock, preventing movement of the point motor when any of the protecting track circuits are occupied. This lock is in addition to and separate from that on the signal frame lever operating the points. 121 point motors have been provided for this scheme.

*Author's Note. — Future developments will entail removal of this indicator.

SIGNALS.
The running signals are 3 aspect colour light signals giving the indications double red or stop: yellow above a red, proceed with caution and be prepared to stop at the next signal; green, next signal showing either yellow or green.

You will note the double red, and yellow and red aspects. This is due to the provision of a red marker light carried from 2' 6" to 5' below the main red light. This subsidiary red light provides a distinctive reminder to the driver that he is in territory where multiple aspect signals are in use. The marker light also serves as an alternative danger signal in the event of the main red light failing. Further, by using it along with the yellow light all risk of a red being mistaken for a yellow is eliminated

Where multiple aspect signals lead into a manual block section no red marker light is provided and this gives indication to a driver that he is leaving multiple aspect territory and entering a manual block section.

Where permissive working is in force, as throughout the St. Enoch Yard area and Saltmarket triangle, calling-on signals are provided. These comprise a red and yellow light unit carried under the main running signal. The yellow lens is a small one and its indication is given along with the main red light above it.

As already explained one lever operates both running and calling-on indications the latter being selected when one or more of the track circuits is occupied between it and the next signal ahead.

Banner signals are provided as ground signals for shunting movements. Each banner signal is illuminated at night by two 15 watt lamps the switch for these being under control of the signalman.

The lamps used in the various light signals are as follows : Main running signals—12 watts.
Two aspect shunt signal— 4 pin lights, each 9 watts. Wrong line indication for do.—25 watts.

The main signal lights are clearly visible in sunshine up to about 1,000 yards and penetrate even the densest, fog thus disposing of the need for fogmen.

Where lack of headroom exists a "searchlight" pattern signal is used having in addition to the marker light only one other light. The three light indication in this case are given on a vane with coloured screens moving in front of the latter light. The automatic signals on No. 2. 3 and 4 platforms and Nos. 9, 10, 11 and 12 platforms rear starting signals are of this type.

Pulling a signal lover does not necessarily alter its indication from red. the change of colour indication being subject, to control from the track circuits ahead and/or the indication given by the next signal ahead, with in some cases a further proviso that an approach track circuit must, be occupied when the signal ahead is red or when the signal ahead is at red with points set for a crossing movement and certain track circuits occupied.

All multiple and 2 aspect signals have their "clear" indications changed to red immediately the complete train has passed clear of the signal and its approach track circuit. This prevents a. signal being put to danger before the engine of a propelling train has reached it, and when an indication is so changed to red it remains at red until the operating lever has been restored to normal and pulled a second time.

The positions of the various signals have been mostly determined by the permanent way lay-out, platform ends etc.

At diverging points where a single signal applies to all routes a route indicator has been provided beside the signal concerned and this indicates by either letter or number the route to be traversed.

Throughout St. Enoch Yard area, signals are provided for wrong-line movements and on the Down Lines these movements are permitted out on to the Clyde Bridge. To trap any train overrunning, catch points with a sand drag have been laid down immediately south of the Clyde Bridge, and in addition elevated "Limit of Shunt" signals have been provided to mark the termination of movements of this kind.

The total number of signals of each type is as follows:—

(d) BRAIN.—SIGNAL FRAME.
The frame consists of a set of 203 levers (180 working and 17 spare levers) and is unique in being the first all electrically interlocked frame introduced on the L.M.S Railway. Each lever is fitted with 2 electric locks, one for normal locking (lever back in frame) and one for reverse locking (lever full over). These locks are also used for check locking the levers to both normal and reverse positions. Every lever in the frame has behind it an illuminated indicator showing the position of the points or outdoor indication of the signal it controls. The indications given are as follows

In the case of selected signals all yellow and green indications are repeated separately on the lever indicators but the red lights have one common indicator. Each route indicator has a square shaped repeater behind its signal lever and this repeater lights up when the route indicator displays a route indication to the driver. It does not repeat each outdoor route indication separately as routes are checked up by relative buttons as described later.

No point lever can be pulled, or once pulled fully restored to normal, unless in all cases the points it controls have properly closed and in the case of facing points, the bolt is in the "In" position. This is done as follows:- The point lever which gives a total applied stroke of 120 degrees to its electrical contacts is pulled over to a fixed position which gives an imparted travel of 70 degrees to the contacts and there the lever remains electrically locked until such time as the energy allowed to flow by this part pull has operated the point motor, moved the points correctly and if necessary bolted them, then and then only, can the lever be pulled to the full over position to free the interlocking and so clear the signal levers. In putting a point lever back to normal the converse applies, -i.e. the lever is checked after the equivalent, of 70 degrees of travel until such time- as the point movement is completed. Levers locked thus are said to be checked locked.

Signal levers can be pulled fully over once their route is set up but only go back to the 70 degrees position until the signal light indication changes to red, or in the case of banner signals, the arm goes to the "On" position.

To sum up therefore. by this mode of check locking levers. We "prove the road," i.e. the completion of the lever movement is an indication that the points have been moved correctly and have been bolted and that signal light indications have gone to red.

In addition to the foregoing we have acting on each lever the following:-

(1) “MECHANICAL'' INTERLOCKING (DONE ELECTRICALLY).
This is the usual interlocking to ensure that lever's are pulled in correct sequence and conflicting routes eliminated.

(2) TRACK CIRCUIT LOCKING.
Point levers are locked by the occupancy of track circuits marking the points they operate and this locking can be applied to the normal or reversed position of the lever, or to both positions. Where no calling-on signal is provided the lever operating a 3 aspect signal is locked in the normal position by the occupancy of any track circuit between the signal in question and the next one ahead.

The levers operating signals into the Gorbals Station end of the Relief Siding and banner signals applying out to the wrong road at the Clyde Bridge are also locked by the track circuits ahead, but in all other cases these signals are used for permissive working purposes and their operating levers must be left free of track circuit control.

(3) SECTIONAL RELEASE ROUTE LOCKING.
Pulling a signal lever plus the occupancy of the track circuit immediately ahead of the signal operated sets up what is known as sectional release route locking and this locking holds all the point levers of the route governed by this signal either in the reversed or normal position. The point levers so locked are only released by the withdrawal of the train from the route, or are released sectionally and in sequence, lever by lever, as each of the protecting track circuits is occupied and then cleared by the forward progression of the train. This locking is provided on all levers operating three aspect signals and on certain of the levers operating two aspect signals where these apply for wrong road movements. It does not apply to levers operating banner signals.

(4) APPROACH LOCKING,
All levers operating multiple aspect or two aspect signals are "approach" locked by occupancy of the track circuit immediately on the approach side of the signal, that is to say, once the lever is pulled and the approach track circuit occupied it can only be restored to the check locked position (70 degrees) in the first instance. Thereafter, as the locking operates automatically through a time element relay, if remains in being for a predetermined period of time - maximum one minute - and the lever can only be fully restored when the time element relay has completed its work, or the approach track circuit, cleared, as the clearing of the approach
track circuit at once nullities the action of the time element relay. This approach locking prevents the movement of points in face of an approaching train, since with a signal lever in the check locked position conflicting point levers are held by the interlocking.

(5) POINT DETECTION.
Signal levers stand normally locked until such time as their route has been set up and are only free to be pulled when the correct point levers have been operated and all points over which the signal applies in the facing direction have been properly closed and bolted. In the event of points being damaged by derailment, overrun, etc., all signals detected through the damaged points will go to danger and the levers operating them will be locked in the normal position.

From the foregoing it will be seen that the "brain" is the correct description to apply to (lie signal frame. It may be of interest to note that on one of the English Lines provided with similar equipment, the electric locks were "picked" and all levers pulled; all signals at once gave a danger indication thus proving the "intelligence" of the brain.

SPECIAL FEATURES.
In terminal stations there are always many special features which cannot be described under the usual signalling equipment headings and these I will now deal with.

(a) AUTOMATIC SIGNALS.
Water columns are provided on Nos. 2, 3 and 4 platforms on the station side of the platform starting signals and trains frequently stand in rear of these signals but ahead of the platform rear starting signals. As these starting signals each stand inside of a fouling point it will be obvious, that if uncontrolled approach is allowed under the foregoing con¬ditions, there is a danger of a driver drawing forward to one of these starting signals whilst a crossing movement is in progress ahead of him. To obviate any risk of accident automatic signals giving a normal red indication have been provided. The "clear " indications are controlled by the indication of the signal ahead, but, if that signal is at red, then the automatic signal indication is only changed to yellow when the approach track circuits are occupied : also when this point has been reached the levers operating the point for a crossing movement are held for a fraction of a minute by a time element relay, thus preventing simultaneous and conflicting movements being made

(b) SIGNAL REPEATERS.
These have only two aspects, normally showing a yellow indication when their controlling signal is at danger this changing to green when the controlling signal shows yellow or green.

On the Saltmarket Branch fish-tailed banner signal repeaters are provided on posts for ingoing traffic. These are controlled through the lights of the signals and the track circuits ahead and only go to the clear position when the roads are clear to the buffer stops in Nos. 1 and 2 Platforms and to the termination of the track circuiting in No. 1 Mid road.

(c) Nos. 7 AND 8 PLATFORMS—STARTING SIGNALS.
These are duplicated, as trains frequently extend beyond the end of Nos. 7 and 8 Platforms. The rear signals mark the fouling and splitting points at Nos. 7 and 8 platforms respectively.

(d) OPERATION OF LEVERS WORKING SELECTED SIGNALS
After operating the necessary point levers the lever working the signal applying over the route remains electrically locked until release is obtained by pressing the requisitely labelled route button placed behind the signal lever. If a wrong route is set up then the signal lever remains locked and this arrangement acts as a definite reminder to the signalman when an error has been made.

The entire supply of electrical energy for the complete installation is obtained from the Glasgow Corporation, two alternative services being available.

In conclusion, my thanks are due to the responsible con¬tractors, Messrs. The Westinghouse .Brake and Saxby Signal Coy., for the use of the lantern slides shown to-night.

Follow this link to obtain larger detailed drawing of St Enoch Station area in PDF format

Follow this link to obtain larger detailed drawing of the Clyde and Gorbals station area in PDF format

Copyright © Mark Adlington 2005-2017
Last modified: