S1 Basics of Signal Engineering PDF

 S1 BASICS OF SIGNAL ENGINEERING Issued in November 2009 INDIAN RAILWAYS INSTITUTE OF SIGNAL ENGINEERING & TELECOMMUNICATIONS SECUNDERABAD - 500 017  S-1 BASICS OF SIGNAL ENGINE...

 S1 BASICS OF SIGNAL ENGINEERING Issued in November 2009 INDIAN RAILWAYS INSTITUTE OF SIGNAL ENGINEERING & TELECOMMUNICATIONS SECUNDERABAD - 500 017  S-1 BASICS OF SIGNAL ENGINEERING CONTENTS S.No Chapter Page No 1 Role of Signalling in Railway operation 1 2 Definitions (GR 1.02) 2 3 Signalling Concepts 7 4 Fixed Signals, Kinds, Aspects & Indications (GR.3.02-3.08) 9 5 Designation of Signals 21 6 Location of Signals 24 7 Subsidiary Signals, Repeaters, Indicators, Markers & Back Lights 31 8 Overlaps 49 9 Breaking Distance 53 10 Sighting Distance & Visibility of Signals 55 11 Isolation 58 12 Simultaneous Reception and Despatch of Trains 62 13 Systems of working 65 14 Classification of Stations – Comparison of A, B & C 76 15 Standards of Interlocking 82 16 Operation of Points 89 17 Inter Cabin control 91 18 Level Crossing Gates 93 19 Section capacity 107 20 Principles of Signal Engineering 109 21 Annexure 1: Intermediate Sidings 111 Drafted By M.D.Dixit, IES-7 Checked By S.V.Rao, PS Approved By Ch.Mohan, SPS DTP and Drawings G.Rajagopal, SE (D) No. of Pages 115 Date of Issue November, 2009 Version No A2 © IRISET “ This is the Intellectual property for exclusive use of Indian Railways. No part of this publication may be stored in a retrieval system, transmitted or reproduced in any way, including but not limited to photo copy, photograph, magnetic, optical or other record without the prior agreement and written permission of IRISET, Secunderabad, India” http://www.iriset.ac.in  INTRODUCTION CHAPTER 1: ROLE OF SIGNALLING IN RAILWAY OPERATION 1.1 Railway Signalling and Communication Technology, though evolved primarily for safe working of trains, plays an important part in increasing line capacity with minimum investment. With the advent of computers and extended communication network on the Railways, the scope of Signalling Technology has widened to incorporate even automatic operation. The broad areas of Railway Signalling and Communication Technology are: 1.2 Block Working Trains are to be adequately spaced apart to prevent collision between trains running in the same direction and prevent trains entering on the same track from the opposite direction. This is achieved by block working between stations. 1.3 Interlocking When trains are to be crossed or overtaken at stations, points and signals are to be worked in proper sequence to make passage of trains safe and interlocking between points and signals takes care of this. Interlocking also safeguards simultaneous movements in stations. Semaphore signals are worked by single wire, double wire or electric motors. Colour light signals are provided for improved visibility, easier working and maintenance. Points are worked by rod, double wire, pneumatic/hydraulic or electric power. Interlocking between point levers and signal levers can be effected either mechanically by means of tappets or locking electrically by means of electric lever locks or relays. With Route Relay Interlocking, a complete route can be set by one operation and suitably safeguarded against conflicting moves. 1.4 Train detection Track circuits can detect the presence of a train on a portion of track or axle counters and this information is used for controlling the signal, which in turn controls the train movements. 1.6 Automatic Warning System As an aid to the driver to know the condition of the signal and to prevent accidents when the driver ignores the aspect of a stop signal, Automatic Warning System is employed. If the driver, due to any reason, does not act upon a signal, the train is brought to stop by automatic brake application. In addition to warning and stopping, as explained above, the speed of the train is continuously monitored and checked with the information as to the permitted speed, and if the actual speed is different from the permitted speed, corrective action is enforced. 1.7 Centralised Traffic Control and Remote Control Economy is achieved and efficiency is increased by centralising operation of points and signals over a large area or a stretch of line. Remote stations are controlled from a central location over a pair of lines using coded techniques. Such centralised operation also leads to increased line capacity. 1.8 Train Describer The designation and number of trains in a section or line can be displayed to the central control office so that the controller is aware of the position and designation of each train over the section monitored by him. The description is advanced from section to section as the train proceeds. Such train describers are normally used with centralised traffic control, remote control as well as in suburban sections. Page 1 BASICS OF SIGNAL ENGINEERING DEFINITIONS C H A P T E R 2 : DEFINITIONS (GR 1.02) In order that interpretation of various terms remain clear and unambiguous, it is necessary to indicate their meanings precisely. This has been done in respect of common terms used in railway signalling in chapter 1 of “General rule”. Some of the important definitions are mentioned below. 2.1 ACT means the Indian Railways Act, 1989 2.2 ADEQUATE DISTANCE means the distance sufficient to ensure safety. 2.3 APPROACH LIGHTING means an arrangement in which the lighting of signals is controlled automatically by the approach of a train. 2.4 APPROVED SPECIAL INSTRUCTIONS means special instructions approved of or prescribed by the Commissioner of Railway Safety 2.5 AUTHORISED OFFICER means the person who is duly empowered by general or special order of the Railway Administration, either by name or by virtue of his office, to issue instructions or to do any other thing. 2.6 AUTHORITY TO PROCEED means the authority given to the Driver of a train, under the system of working, to enter the block section with his train; 2.7 AXLE COUNTER means an electrical device which, when provided at two given points on the track, proves by counting axles in and out, whether the section of the track between the said two points is clear or occupied; 2.8 BLOCK BACK means to despatch a message from a block station intimating to the block station immediately in rear on a double line or to the next block station on either side on a single line, that the block section is obstructed or is to be obstructed; 2.9 BLOCK FORWARD The block section in advance is obstructed or is to be obstructed; 2.10 BLOCK SECTION means that portion of the running line between two block stations on to which no running train may enter until Line Clear has been received from the block station at the other end of the block section. 2.11 CENTRALISED TRAFFIC CONTROL means a system by which the working of trains over a route, to which the system applies, is governed by fixed signals remotely controlled from a designated place. 2.12 COMMISSIONER OF RAILWAY SAFETY means an official appointed to exercise any functions under the Act, and includes a Commissioner of Railway Safety; 2.13 CONNECTIONS When used with reference to a running line, means the points and crossings, or other appliances used to connect such line with other lines or to cross it. 2.14 COMPETENT RAILWAY SERVANT Means a railway servant duly qualified to undertake and perform the duties entrusted to him. 2.15 CONTROLLER Means a railway servant on duty who may for the time being be responsible for regulating the working of traffic on a section of a railway provided with the system of speech communication. 2.16 DAY means from sunrise to sunset. IRISET Page 2  DRIVER 2.17 DRIVER means the engine driver or any other competent railway servant for the time being incharge of driving a train. 2.18 DIRECTION OF TRAFFIC means (a) On a double line, the direction for which the line is signalled; (b) On a single line, the direction for the time being established, under the system of working, to allow trains to move in that direction; 2.19 ELECTRICAL COMMUNICATION INSTRUMENT means either a telephone or a Morse Telegraph instrument; 2.20 FACING AND TRAILING POINTS Points are facing or trailing in accordance with the direction a train or vehicle moves over them. Points are said to be facing points when by their operation a train approaching them can be directly diverted from the line upon which it is running. 2.21 FIXED SIGNAL means a signal of fixed location indicating a condition affecting the movement of a train and includes a semaphore arm or disc or fixed light for use by day and fixed light for use by night. 2.22 FOULING MARK means the marks at which the infringement of fixed Standard Dimensions occurs, where two lines cross or join one another. 2.23 GANGMAN Means a railway servant employed on permanent way or works connected therewith Or Means a competent railway servant posted at a level crossing for working the gates. 2.24 GANG Means the person in charge of a gang of workmen employed on permanent way or works connected therewith. 2.25 GOODS TRAIN Means a train (other than material train) intended solely or mainly for the carriage of animals or goods. 2.26 GUARD Means the railway servant in charge of a train and includes a Brakesman or nay other railway servant who may for the time being be performing the duties of a Guard. 2.27 INSPECTOR OF WAY OR WORKS means any Inspector or Assistant Inspector responsible for the construction or maintenance of permanent way, points and signals, bridges or other works connected therewith. (This is now re-designated as Section Engineer (works)). 2.28. INTERLOCKING means an arrangement of signals, points and other appliances, operated from a panel or lever frame, so interconnected by mechanical locking or electrical locking a fixed stop signal in IBS or both that their operation must take place in proper sequence to ensure safety. 2.29 INTERMEDIATE BLOCK POST means a class `C' station on a double line, remotely controlled from the block station in rear. 2.30 INTERMEDIATE BLOCK SIGNALLING means an arrangement of Signalling on double line in which a long block section is split into two portions each constituting a separate block section of a block section by providing an Intermediate Block Post. 2.31 ISOLATION means an arrangement, secured by the setting of points or other approved means, to protect the line so isolated from the danger of obstruction from other connected line or lines. Page 3 BASICS OF SIGNAL ENGINEERING DEFINITIONS 2.32. LAST STOP SIGNAL means the fixed Stop Signal of a station controlling the entry of trains into the next block section. 2.33 LEVEL CROSSING means the intersection of road with railway track at the same level. 2.34. LEVEL CROSSING GATE Means any form of movable barrier, including a chain, capable of being closed across the road at the level crossing but does not include a wicket or a turnstile for the use of pedestrians. 2.35 LINE CLEAR means the permission given from a block station to a block station in rear for a train to leave the latter and approach the former; or the permission obtained by a block station from a block station in advance for a train to leave the former and proceed towards the latter. 2.36 LOCO PILOT Means the Loco Pilot or any other competent railway servant of the time being in charge of driving a train. 2.37 MAIN LINE means the line ordinarily used for running trains through and between stations. 2.38 MATERIAL TRAIN Means a departmental train intended solely or mainly for carriage of railway material when picked up or put down or for execution of works, either between stations or within station limits. 2.39 MIXED TRAIN means a train intended for the carriage of passengers and goods, or of passengers, animals and goods. 2.40 MULTIPLE ASPECT SIGNALLING means a Signalling arrangement in which signals display at any one time any one of the three or more aspects and in which the aspect of every signal is pre-warned by the aspect of the previous signal or signals. 2.41 NIGHT means from sunset to sunrise. 2.42 OBSTRUCTION and its cognate expressions include a train, vehicle or obstacle on or fouling a line, or any condition which is dangerous to trains. 2.43 OVERHEAD EQUIPMENT Means the electrical conductors over the tracks together with their associated fittings, insulators and other attachments by means of which they are suspended and registered in position for the purpose of electric traction. 2.44 PASSENGER TRAIN Means a train intended solely or mainly for the carriage of passengers and other coaching traffic, and includes a troop train. 2.45 POINT AND TRAP INDICATORS are not signals, but are appliances fitted to and working with points to indicate by day or by night the position in which the points are set. 2.46 RUNNING LINE means the line governed by one or more signals and includes connections, if any, used by a train when entering or leaving a station or when passing through a station or between stations. 2.47 RUNNING TRAIN means a train, which has started under an authority to proceed and has not completed its journey. 2.48 SHUNTING means the movement of a vehicle or vehicles with or without an engine or of any engine or any other self-propelled vehicle for the purpose of attaching, detaching or transfer or for any other purpose. IRISET Page 4  SPECIAL INSTRUCTIONS 2.49 SPECIAL INSTRUCTIONS means instructions issued from time to time by the authorised officer in respect to particular cases or special circumstances. 2.50 STATION means any place on a line of Railway at which traffic is dealt with, or at which an authority to proceed is given under the system of working. 2.51 STATION LIMITS means the portion of a railway, which is under the control of a Station Master and is situated between the outermost signals of the station or as may be specified by special instructions. 2.52 STATION MASTER means the person on duty who is for the time being responsible for the working of the traffic within station limits, and includes any person who is for the time being in independent charge of the working of any signals and responsible for the working of trains under the system of working in force. 2.53 STATION SECTION: Pl see Chapter No- 14. 2.54 SUBSIDIARY RULE means a special instruction, which is subservient to the General Rule to which it relates and shall not be at variance with any General Rule. 2.55 SYSTEM OF WORKING means the system adopted for the time being for the working of trains on any portion of a railway. 2.56 TRACK CIRCUIT means an electrical circuit provided to detect the presence of a vehicle on a portion of track, the rails of the track forming part of the circuit. 2.57 PASSENGER TRAIN Means a train intended solely or mainly for the carriage of passengers and other coaching traffic, and includes a troop train. 2.58 TRAIN EXAMINER Means a railway servant duly qualified to examine trains and certify their fitness for safe running and includes and their railway servant who may for the time being be performing the duties of Train Examiner. 2.59 TWO-ASPECT SIGNALLING means a Signalling arrangement in which each signal displays at any one time either of the two aspects. 2.60 CLASSIFICATION OF STATIONS (a) Stations, shall for the purpose of these rules, be divided into two categories - block stations and non-block stations. (b) Block stations are those at which the Driver must obtain an authority to proceed under the system of working to enter the block section with his train; and under the Absolute Block System consist of three classes viz. `A', `B', `C', etc (see Chapter 14). 2.61 COLOUR LIGHT SIGNAL A fixed signal in which the indications are given by the colour of a light only. 2.62 EMERGENCY BRAKING DISTANCE is the distance travelled by train before coming to a stop by sudden application of brake at one stretch. 2.63 IN REAR OF A SIGNAL means the territory over which an approaching train has to pass before reaching the signal location. 2.64 IN ADVANCE OF A SIGNAL A term used in defining a territory beyond a signal as seen from the approaching train. Page 5 BASICS OF SIGNAL ENGINEERING DEFINITIONS 2.65 LINE CAPACITY means the maximum number of trains that can be run on any given section during a calendar day of 24 hours. 2.66 OVERLAP means the length of track in advance of a stop signal, which must be kept clear, either for clearing the stop signal next in rear or for the purpose of granting permission to approach. 2.67 `ON' ASPECT means the most restrictive aspect of the signal. 2.68 `OFF' ASPECT means any aspect other than the `ON' aspect of a signal. 2.69 POSITION LIGHT SIGNAL A fixed signal in which the indications are given by the position of two or more lights. 2.70 SEMAPHORE SIGNAL A signal in which the day indications are given by the position of a semaphore arm. 2.71 SERVICE BRAKING DISTANCE is the distance required to stop the train running at the maximum permissible speed of the line, at such a rate of deceleration that the passengers do not suffer discomfort or alarm. Review questions 1. Under special instruction means approval from commissioner of railway safety. (False/ True) 2. Under approved special instruction means approval from authorized officer. (False/ True) *** IRISET Page 6  INTRODUCTION CHAPTER 3: SIGNALLING CONCEPTS 3.1 INTRODUCTION Railway vehicles move on Steel Rail Track and are provided with flanged steel wheels. The rolling of the steel wheel on steel rail has the least friction and it is, therefore, one of the most efficient means of locomotion. 3.2 Control over movement of Trains Running of flanged vehicles on the steel track has its own inherent problems unlike the road, sea or air transport where the movement is not confined to a particular track. Since the vehicles are constrained to move in a fixed Railway track, they cannot be steered away as in the case of other transports. They are required to follow one another in the same direction on the length of track, as otherwise for every vehicle separate parallel paths are to be provided. This is not practicable. If vehicles are expected from the opposite direction another set of diversion track is required to be provided either for overtaking vehicles moving in the same direction or for crossing the vehicles from the opposite direction. Railway locomotion, therefore, though more efficient, brings in problems of "Control over movement of Trains". Basically, two types of controls could be catered for. If two separate tracks are provided for trains running in opposite directions, then one set of control can be provided to space the movement of trains running in the same direction so that adequate "interval" is available between two consecutive trains. On the other hand, if a single track is used for movement of trains in both directions, then another set of control is required to prevent a train in the opposite direction from coming on the same track when a train is already occupying it. 3.3 Time Interval Method Let us take the first case of spacing of trains in the same direction. The spacing should be such that if a train stops, then, the following train driver should be able to notice it and apply brake to his train so that it stops short of the preceding train. The most important aspect is bringing to a stop from the speed at which a train is running. Where the speeds and weights are low, it is not difficult for a following train to stop short of the train ahead, which has stopped. This is how tramways operate even today, as the speed and weight are low and a tram can be stopped from its running speed without colliding with a tram in front. With higher speeds and heavier loads, as in the case of Railway train, the distance required to stop a train is longer, and at this longer distance, the driver cannot definitely decide whether a train in front has actually stopped or not. This is the case when trains follow one another in quick succession. In actual practice, where interval between trains is longer, a following train does not see the earlier train, and the driver has to continuously guess as to where the earlier train will be. If all trains run at the same speed and are required to stop at the same place for the same duration, a certain amount of control can be exercised by having a definite time lag between the trains from one stopping place to another. This time lag should be such that the train, which has a stop, is able to reach the next stop within this time. Thus by having a time interval between trains, a certain amount of control can be achieved. But, in the case of Railway, this is not practicable, as - (a) Different types of trains like, Express/Mail, passenger, high-speed freight and low speed freight shunting trains are running etc. (b) The speed of all the trains are not same (c) The terrain of the country is not same everywhere (d) The brake power, hauling capacity, load of train is not same for all trains; and (e) The stopping places of all trains are not the same Hence, it is not possible to control the movement of trains under the "Time interval method". A better method of control is called the "Space Interval Method" is adopted. Page 7 BASICS OF SIGNAL ENGINEERING SIGNALLING CONCEPTS 3.4 Space Interval Method In this method of "Control over movement", the length of track is divided into sections called "Blocks". The entry of a train into the ‘block’ is controlled in such a way that only when it is free, a train can be allowed to enter it. This means that between two consecutive trains, there is a definite space interval. This space interval or block is controlled at the entry. This controlling point should know whether the train, which had entered this space, vacated it so that another following train can be sent. Since the length of a block is beyond the normal visual range, another controlling point is set at the end of the block. This point can know whether the train has arrived and advise the controlling point at the entry. So, with the two controlling points and intercommunication, it is possible to control the entry of a train into a block only when it is vacant. The information about the condition of this block is given by the exit point to the entry point, and the entry point transmits this information to the driver of a train. The driver of the approaching train must be able to know whether the next block is not clear, he should stop and wait. Here is where "signal" comes in to picture. 3.5 Signals A "Signal", therefore, is a medium to convey a particular pre-determined meaning in non- verbal form. Various methods are used to convey the meaning by "Signals" in a non-verbal form as are used by Scouts, Policemen, road signs, Navy and Air Traffic Control, etc., which convey a definite information. The chart below gives the various forms that could be adopted. SIGNALS VISUAL AUDIBLE Movable Flag Fixed Flare Detonators Voice Whistle Signal Signal Signal Running Subsidary Two Aspect Multiple Aspect Miniature Arm Disc Position Light CLS (TAS) (MAS) Type Type Type Type Semaphore CLS Semaphore CLS 3.6 Block Working As explained earlier, the space interval system uses the block working wherein the entry of train onto the block section is jointly controlled by the entry and exist points of the block section. The driver is authorised to proceed into a section by the signal controlling the entry to the section. This working could be a manual block system or automatic block system. In any type before the train could be allowed to enter a section "PERMISSION" is required to be obtained from the Exit end to the effect that the section is "CLEAR" of trains and the train could be permitted. Different systems of working for getting this “PERMISSION TO APPROACH” have been evolved on Indian Railways and are classified as "System of Working". The details of system of working are explained in Chapter 13. 3.7 Thus it can be concluded from the above general description of concept of Signalling that the main purpose of Railway Signalling Systems is to maintain a safe distance between trains on the same track. IRISET Page 8  INTRODUCTION CHAPTER – 4: FIXED SIGNALS, ASPECTS & INDICATIONS (GR.3.02-3.08) 4.1 In Chapter 3, a mention was made about the use of different types of visual and audible signals, for controlling the movement of trains in all cases. No exceptions are allowed by approved special Instructions in the following: (a) Fixed Signals (b) Hand Signals (c) Detonating Signals (d) Flare Signals 4.2 The definition of "Fixed Signals" as given in the General Rules is "a signal of fixed location indicating a condition affecting the movement of a train and includes a semaphore arm or disc or fixed light for use by day and a fixed light for use by night”. 4.3 Semaphore signals used on the Railways are in the form of a rectangular or fish tailed arm fixed to a vertical post. The arm is kept horizontal to the post to be easily distinguishable. By this arrangement the arm can be seen from a long distance on a clear day. Whenever the signal is required to convey some information:- The arm can altogether be removed from the view of the driver by making the arm to disappear in a slot provided on the post; or (a) The arm can be made to assume a mid-way position below horizontal; or (b) To assume a mid-way position above horizontal; or (c) To assume a vertical position parallel to the extended line of the post. 4.4 Method (a) was adopted in the early days and subsequently given up as the absence of arm due to some reason other than it’s entering the slot in the post conveyed wrong information. Methods (b) and (c) above could be on the Right hand side or left hand side of a Quadrant as shown below in (Fig. 4.4). Fixed Signals can operate on any one of the four quadrants of a circle as shown. Since `Left hand' rule is followed in India, the "lower quadrant" and "Upper quadrant" of the left hand side is utilised in Indian Railways. Based on this principle, signals are also generally located on the left side of the track. R PE UP IN AN T T DR N Q U A EME M OV LH RH UQ UQ LH RH IN NT E NT LQ LQ L O A DR A R WE EM QU O V M Fig. 4.4 Use of Quadrant Page 9 BASICS OF SIGNAL ENGINEERING FIXED SIGNALS, KINDS, ASPECTS & INDICATIONS 4.5 It can be seen in the figure above that an arm in a lower quadrant can have only two positions, one at horizontal position and the other at midway position on the left-hand side. In Upper Quadrant, three positions can be obtained, i.e. one at horizontal position, one at midway position and the 3rd at vertical position in parallel with the extended line of post. Hence, we have two systems of signalling, one called "Lower Quadrant Signalling" and the other called "Upper Quadrant Signalling". 4.6 Two aspect Lower Quadrant Signalling (a) Stop-signal (reference SEM 17.115.1) The semaphore arm of the stop signal is square ended, painted Red with White bar parallel to the square end in front and painted white with black bar in rear. As explained, a lower quadrant signal can show only two different positions. One is horizontal and the other lowered to midway position. They are called "aspects" of the signals. The movement of the signal arm in lower quadrant is generally adopted by countries where there is no snowfall or other external conditions which can result in the arm remaining lowered without being operated. The arm in the horizontal position will convey an aspect "stop" indicating "Stop dead". The arm lowered to midway position in the lower quadrant will convey an aspect "proceed", indicating Proceed. Semaphore arm can be seen during day and so can convey information during daytime. At night the arm will not be visible. Hence, to convey information during night, fixed light signals are used. Right from the early days, red lights were used to denote "Stop" and green lights were used for "Proceed". Red light should, therefore, be exhibited when the arm is horizontal and green light when the arm is inclined midway. A semaphore signal is a combined integrated unit with an arm and light. The horizontal position of the arm during daytime is considered as the `ON' aspect and the inclined position is the "OFF" aspect of the signal. The corresponding light Red & Green during nighttime are `ON' and `OFF' aspects respectively. The `ON' aspect of a signal is also referred to as the most restrictive aspect. The figure 4.6(a) shown below will give the details of the aspect and indications for two-aspect semaphore signal. ASPECT & INDICATION FOR TWO ASPECT L OWER QUADRANT STOP SIGNAL ASPECT STOP PROCEED INDICATION STOP DEAD PROCEED Fig. 4.6 (a) Two-Aspect Semaphore Stop Signal (Lower Quadrant (reference SEM I7.115.2) IRISET Page 10  TWO ASPECT LOWER QUADRANT SIGNALLING (b) WARNER SIGNAL Two-aspect stop signal as explained above is the minimum required to safely space the trains. This is adequate for low speeds and low density of traffic. Safety depends on the driver seeing the signal in time under all conditions. This imposes an enormous strain on the driver who has to be constantly on the lookout, to pick up the signals. Any mistake or loss of attention can lead to serious consequences. Otherwise drivers will play safe by running at lower speeds so that he can stop at the signal even if he sees it at the last minute. With such low speeds, the time of occupation of the block sections by the trains will increase, thereby reducing the number of trains per day that can be run between the block stations. One method of overcoming this problem will be to give advance information, or "WARNING" to the driver about the presence of stop signal ahead and the aspect displayed by the stop signal. This can be achieved in the form of another signal. This signal can precisely inform the driver that he is approaching a stop signal and also that he is required to stop or proceed. The signal which gives such warning about the condition of the stop signal ahead is called a "WARNER SIGNAL". Since the driver is not required to stop at the Warner Signal, as it is only giving an advance warning about the presence of the stop signal ahead, this signal has to be different from the stop signal. The day aspect, therefore, is characterised by a fish tailed arm instead of a square ended arm. This is also a two aspect Lower Quadrant Signal. Since the Warner Signal is not a stop signal and is exhibiting Red Light when `ON’ this should be distinguishable from a Stop Signal during night. This is done by mounting the arm at a lower level in the post and providing a separate additional fixed Green Light at 1.5 to 2.0 metres above the arm. This combination of Green Light above a Red Light distinguishes a signal as a Warner Signal in the `ON' position. When the signal is lowered to midway position, the Red Light changes to green and the Driver sees two green lights one above the other. The aspect and indications of the Warner Signal on a post by itself is shown in Fig. 4.2 (b). Two precise informations are given to the driver by the Warner Signal. When the arm is horizontal during day and showing of a Green Light and Red Light below during nighttime indicates to the driver that he can proceed, but must be prepared to stop at the next Stop Signal. Similarly, the lowering of arm during day and showing of two Green Lights one below the other during night indicates that he can proceed and can expect all the stop signals ahead of Warner for that direction are OFF and he can run through main line. 4.7 A Warner signal must not be capable of being taken `OFF' for any line other than that over which the highest speed is permitted (i.e. main line) and not until all the relevant signals have assumed `OFF' aspect. The last of the stop signals will be the one controlling the entry of the train in the block section ahead. Even if any one of the stop signals ahead is `ON' the Warner cannot display `OFF' aspect. Page 11 BASICS OF SIGNAL ENGINEERING FIXED SIGNALS, KINDS, ASPECTS & INDICATIONS 4.8 Under certain circumstances a semaphore Warner signal is required to be placed on the same post of a stop signal. In such cases, the Warner signal is placed below the Stop Signal, and the fixed green light is dispensed with. ASPECT AND INDICATION OF LOWER QUADRANT SEMAPHORE WARNER SIGNAL aspect Proceed with Caution proceed Indication Proceed with caution & proceed be prepared to stop at next stop signal Fig. 4.6 (b) Semaphore Two-Aspect - Warner Signal on a Post by Itself (Lower Quadrant) 4.9 The combination of two arms (Stop and Warner) on the same post gives the driver three indications in the 2-aspect lower quadrant signalling. When both the Stop Signal and the Warner Signal arms are at horizontal position and the showing of two Red Light one below the other gives an indication to the driver to `Stop dead' at this signal. The lowering of the Stop Signal above the Warner or showing of a Green Light above a Red Light indicates that he can proceed past the signal with caution and be prepared to stop at the next stop signal. A third condition exists when both the arms are lowered to give two Green lights one below the other. This indicates to the driver that he can proceed and can expect all the stop signals for that direction are `OFF' and that the block section ahead is also clear. It is also made mechanically impossible to lower only the Warner Signal when the stop signal above it is `ON'. In this way showing of Green Light below a Red light is eliminated. The details of the signals and aspects are shown in figure 4.9 below. ASPECT AND INDICATION OF WARNER BELOW STOP SIGNAL Aspect Stop Proceed with caution proceed Indication Stop dead Proceed with caution proceed & be prepared to stop at next stop signal Fig.4.9 Semaphore Two-Aspect - Warner below a Stop Signal IRISET Page 12  MULTIPLE ASPECT UPPER QUADRANT SIGNALLING 4.10 A comparison between a Warner Signal on a post by itself and a Warner Signal below a Stop Signal is as follows (a) The night aspect of a separate Warner when `ON' is a green light above a Red Light. If the Red Light gets extinguished for some reason or other, it will give only a Green Light to a approaching driver and he can mistake the signal to be a stop signal in the `OFF' position and can `Proceed' instead of going cautiously. (b) On the other hand if the fixed green light gets extinguished, the night aspect will only be a "RED" light exhibited which can be mistaken for a "Stop Signal" in `ON' position. This will be noticed only when the driver comes nearer to the signal and he sees a Fish tailed semaphore arm instead of a square ended arm. (c) Pre-warning to the driver of an approaching train can be given only when a Warner Signal is placed on a post by itself and this will enable the driver to control his train suitably. (d) In the case of a Warner Signal placed below a Stop Signal the night aspect in the `ON' position is showing of two Red Lights one below the other. Even if any one of the lights gets extinguished, the other Red light will be available which will still indicate to the driver that it is a stop signal. If the stop signal above the Warner, is lowered and the green light gets extinguished then a Red Light of Warner will be visible. However, he could be governed by the stop signal arm above the Warner arm as he comes near the signal, and be guided by it. (e) In the case of a Warner Signal placed below a Stop Signal, no pre-warning is available for the stop signal. As explained earlier, the `ON' aspect of a Warner signal on a post by itself, tells the driver that he should proceed cautiously and can expect the next stop signal is in the `ON' or `OFF' position. Hence he is required to pass the signal at a reduced speed (when at `ON'). 4.11 From the point of view of the driver, therefore, the `ON' aspect of Warner does not signify positively anything about the signals ahead whereas if such information is available, he can confidently approach the signal ahead. A system of warning about the condition of each signal by a signal in rear is, therefore, very much necessary. This leads to the concept of more than 2 aspects called "MULTIPLE ASPECT SIGNALLING". 4.12 Multiple Aspect Upper Quadrant Signalling (a) Stop Signal: It has been mentioned in previous para that the semaphore arm can be made to assume a midway position above horizontal and also another position in parallel with the extended line of the post on the left hand Upper Quadrant. In this way, it is possible to obtain more than 2 aspects in the Upper Quadrant region and hence, it is called "Multiple Aspect (more than 2 aspects) "Upper Quadrant" signalling as distinct from "two aspect Lower Quadrant Signalling" mentioned in previous paras. The Semaphore Arm in Upper Quadrant is similar to 2-aspect lower quadrant square ended arm, painted Red with white bar in the front and painted white with black bar in rear. Since the signal is required to convey 3 aspects, the arrangements in the "spectacle" are such that 3 different colour glasses, namely, Red, Yellow and Green ROUNDELS can be fixed to convey the night aspects of the signal. The arm in the horizontal position in day will convey `ON' aspect indicating "Stop Dead". The night aspect of the horizontal position of the arm by showing of a Red light. Page 13 BASICS OF SIGNAL ENGINEERING FIXED SIGNALS, KINDS, ASPECTS & INDICATIONS The raising of the semaphore arm to "45 degrees above horizontal" in the left hand Upper Quadrant region will convey an aspect "Caution" indicating "Proceed with caution and be prepared to stop at the next stop signal". The night aspect of the mid-way position by showing of a yellow light. The raising of the arm to 90 degrees above horizontal in parallel with the extended line of post in a vertical position will convey an aspect "Clear" indicating "Proceed" and the next stop signal is also `OFF'. The corresponding night aspect is the showing of a Green Light. The aspects and indications of a Multiple Aspect Upper Quadrant Stop signal are shown in figure 4.12(a) below: ASPECT AND INDICATION OF UPPER QUADRANT MULTIASPECT STOP SIGNAL ASPECT STOP CAUTION PROCEED INDICAT STOP DEAD PROCEED & BE PROCEED ION PREPARED TO STOP AT THE NEXT STOP SIGNAL FIG. 4.12(a) MAUQ - STOP SIGNAL (b) Distant Signal As discussed in the case of 2-aspect signalling when a driver approaches the first stop signal he should be warned about its condition. Therefore, a signal similar to the Warner Signal in the 2-aspect signalling is also a necessity in Multiple Aspect Upper Quadrant signalling. This pre-warning signal is called a "DISTANT" signal. The term `Distant' is used here, as this is the farthest signal from the station on the approach side. The semaphore arm will have 3 positions - horizontal, 45 degrees above horizontal and 90 degrees above horizontal. The arm is fishtailed similar to lower quadrant Warner signal. The front side facing the train is coloured yellow with a black bar parallel to the end and the backside is coloured white with a black bar. According to the convention adopted that the night aspect in the `ON' position should correspond with the colour of the arm the distant signal exhibits a yellow light in the `ON' position during nighttime. The yellow colour and the fish tailed shape of the arm facilitate the driver in distinguishing a `Distant' signal from a "STOP SIGNAL" from a longer distance. The second aspect that is given by the distant signal is the arm raised to 45 degrees during daytime. But for the night aspect, since the yellow aspect is already used for the `ON' aspect of the signal, a special aspect is given by having `two yellow lights' one below the other. This second yellow fixed light below the yellow aspect of the arm should not be visible in any position other than the 45 degrees position. Hence, a mechanical arrangement is made in the working of this signal such that the fixed yellow light gets `blanked out' in all other positions. In this way 2 yellow lights one below the other is exhibited in the 45 degrees positions only. IRISET Page 14  MULTIPLE ASPECT UPPER QUADRENT SIGNALLING The Indications conveyed to the driver are that the next stop signal is `OFF', but he should pass the next Stop Signal at a restricted speed. This aspect of raising the distant arm to 45 degrees position in daytime or showing of 2 yellow lights is the aspect called "ATTENTION". The third aspect given by the distant signal is by raising the arm vertically to 90 degrees position, the night aspect being "GREEN" light, which indicates to the driver that he can proceed and can expect the next signal in the `OFF' is given in Fig. 4.12 (b) below: ASPECT AND INDICATION M.A.U.Q. DISTANT SIGNAL aspect Caution Attention proceed Indication Proceed & be prepared Proceed & be prepared proceed to stop at next stop to pass next stop signal signal at such a speed as prescribed by special instruction Fig. 4.12 (b) MAUQ - DISTANT SIGNAL Fig. 4.12 (c) MAUQ - DISTANT SIGNAL Page 15 BASICS OF SIGNAL ENGINEERING FIXED SIGNALS, KINDS, ASPECTS & INDICATIONS 4.13 The three positions of a Multiple Aspect Upper Quadrant both of a stop signal and a distant signal are horizontal for the `ON' position, raised to 45 above horizontal and raised to 90 Degrees above horizontal are the `OFF' positions. 4.14 It has been mentioned earlier as to how a two aspect stop signal and a Warner can be combined to give 3 aspects. A similar case may occur in Upper Quadrant Signalling also where a signal may have to exhibit 4 aspects, i.e. those of a stop and distant signal. However, the need for such 4-aspect semaphore signals had not been felt very much and no design for such signals had been evolved. Where light signals are used, it is possible to provide a signal exhibiting 4 aspects by combination of lights, which are used in colour light signalling area. 4.15 So far we have discussed two types of signals i.e. Lower Quadrant 2-aspect and Multiple Aspect Upper Quadrant. The Warner/Distant Signals are not stop signals and, therefore, "Permit" the approaching driver to pass the signal in the `ON' position. Hence they are called "Permissive Signals". The stop signals in the 2 aspect and Multiple aspect cannot be passed by the approaching driver in the `ON' position unless and until he is specially authorised. Hence, these signals are called "Absolute Signals". 4.16 The above two types of semaphore signals are 2-aspect lower quadrant and 3-aspect Upper Quadrant whether Permissive signals or absolute signals. The lights exhibited in the nighttime are lighted by "Kerosene Wick Lamps" or by electric lamps and they are lit only during the nighttime. In some areas, where the visibility of arm is very poor due to snow or fog, the night aspects are required to be lit in the day time also. The lighting of the lamps is left to the operating staff. 4.17 Multiple Aspect Colour Light Signals Instead of having an arm by day and light by night it is preferable to have only lights as signals for both day and night and such signals are called Colour Light Signals. These are mainly used in busy suburban sections and main trunk routes, as these require electric power to operate them. Use of colour light signals is essential in the Electrified sections. Some of the advantages of Colour Light Signals over the semaphore signals are: (a) The day and night aspects are the same, therefore no confusion to the Driver. (b) The visibility can be obtained for longer range and the natural background adds to improve the visibility, especially it is excellent in the nights. (c) The signals are placed at driver's eye level. (d) The drooping of signal arm due to snow or external force is completely eliminated. (e) A combination of 4 aspects can be obtained. (f) No mechanical transmission, no moving parts, so no wear and tear, and long range of operation is feasible. (g) No kerosene is required and no necessity to depend on Operating Staff for lighting lamps. The details of the aspects and indications of a Multiple Aspect Colour Light Stop Signal are as shown in Fig. 4.17 (a) and Fig. 4.17 (b). IRISET Page 16  MULTIPLE ASPECT COLOUR LIGHT SIGNALS ASPECT & INDICATION OF MULTIPLE ASPECT COLOUR LIGHT SIGNAL ASPECT STOP CAUTION PROCEED INDICATION STOP DEAD PROCEED & BE PROCEED PREPARED TO STOP AT THE NEXT STOP SIGNAL Fig4.17a Fig.4.17 (b) Note: Where "Distant" and "Inner Distant" signals are provided the Distant shall display only "attention" or "proceed" aspect. (Ref.GR.3.07 & BD’s L.68/W3/SG/5/4 of 5/2/70) Page 17 BASICS OF SIGNAL ENGINEERING FIXED SIGNALS, KINDS, ASPECTS & INDICATIONS 4.18 Similarly the lower quadrant semaphore signals can also be replaced by colour light signals. The aspects and indications in such cases are shown in Figure 4.18 (a), (b) and (c). 'ON' Position 'OFF' Position Aspect: Stop Proceed Indication: Stop Dead Proceed Fig.4.18 (a) 2-Aspect Colour Light Stop Signal 'ON' Position 'OFF' Position P P Aspect: Proceed with Caution Proceed Indication: Proceed with Caution and be Proceed prepared to Stop at next Stop Signal Fig. 4.18 (b) 2-Aspect Colour Light Warner on a Post by Itself 'ON' Position 'OFF' Position Aspect: Stop Proceed with Caution Proceed Indication: Stop Dead Proceed with Caution and be Proceed prepared to stop at next Stop Signal FIG. 4.18 (c) 2-ASPECT COLOUR LIGHT WARNER BELOW A STOP SIGNAL IRISET Page 18  MULTIPLE ASPECT COLOUR LIGHT SIGNALS 4.19 From the above, the aspect displayed by these signals and the indication given to the approaching driver, it can be seen that (a) In the case of 2-aspect lower quadrant, the driver is given only two precise informations at the approach of a station. A Warner Signal at Green (OFF) indicates that he can proceed (run through) at the normal speed and a Warner at `ON' indicates that he has to approach the next signal cautiously, preparing to stop. (b) In the case of Multiple aspect signalling, the driver is not given any precise information about run through at the approach of a station. The distant signal at Green (OFF) indicates that he can proceed and expect the next stop signal to be OFF and further Stop Signals ahead of this may or may not be OFF. (c) 4-Aspect Colour Light Stop Signal at `OFF' with green light, indicates the driver to proceed, next stop signal is also `OFF. Yellow aspect indicates caution and tells the driver to proceed with caution and be prepared to stop at the next stop signal. In addition to the above aspects, a 4-Aspect Stop Signal has an attention aspect by showing of two yellow lights one above the other informs driver to proceed and be prepared to pass the next stop signal at restricted speed. This may be on account of either the train has to negotiate a turn-out ahead or the breaking distance is not being available between next signal at caution and the signal in advance at Red, so that he could control the speed. 4.20 So far we have seen that a minimum of one stop Signal and a Permissive Signal is necessary to provide the requisite space interval between the trains. Trains are normally dealt with at stations for different purposes such as stopping for passengers, for loading, for servicing, etc., in which case the stop signals are required to be located at different locations to cater to the needs. Stop signals could be provided at the approach end of a station and/or at the departure end of the station and/or at converging or diverging junction points at a station. This involves the introduction of calling the stop signals by different names depending upon the location and hence we come to the details of "DESIGNATION OF SIGNALS". Page 19 BASICS OF SIGNAL ENGINEERING FIXED SIGNALS, KINDS, ASPECTS & INDICATIONS Review questions Subjective Questions 1. Write down difference between Warner signal and Distant signal. 2. Write down the advantages of Colour Light Signals over the Semaphore signals. Objective Questions State true OR false 1. Indications for caution aspect is proceed and be prepared to pass next stop signal at restricted speed. (False/ True) 2. OFF aspect of a Warner signal is attention. (False/ True) 3. Name of aspect and indication of UQMA signal and MACL signal are not same. (False/ True) 4. UQ distant signal cannot combine with a stop signal. (False/ True) 5. Warner signal at OFF indicate run through condition on Loop Line. (False/ True) 6. A “P” maker shall be provided bellow UQ distant signal. (False/ True) 7. A Warner signal and a distant signal perform same function. (False/ True) 8. A Warner signal (semaphore) is permissive signal and provided with a “P” marker. (False/ True) 9. A Warner signal on independent post at ON provides information regarding aspect of signal in advance (False/ True) Fill up the blanks 1. If distant signal in single distant territory display proceed aspect then it indicates ______________________ a) Run through on main line b) Run through on loop line c) Train is going to be received on Main line d) all a,b &c 2. The possible maximum numbers of aspect in LQ signal with combination of signal is/ are _________________ a) Stop b) proceed with caution c) proceed d) all a,b,&c 3. Total aspect in distant signal in double distant signal territory is/ are a) Attention b) a &c c) proceed d) caution *** IRISET Page 20  SIGNALS FOR RECEPTION CHAPTER 5: DESIGNATION OF SIGNALS 5.1 At a block station it is obligatory to provide certain number of signals for controlling the movements of trains. There we require some signals to deal with the trains approaching the station and some to deal with departure of trains from the station. When more than one stop signals are used a difficulty to identify them from each other will arise. Hence it is necessary to give some name to these signals. 5.2 SIGNALS FOR RECEPTION: Signals, which are governing the approach and entry of trains into a station, are, (a) PERMISSIVE SIGNALS: A "WARNER' in case of 2-Aspect signalling can be placed below the first stop signal or below the Last Stop Signal or can be on a post by itself with fixed green light above. It is to warn the driver that he is approaching a stop signal or to warn him about the condition of block section ahead. In multiple aspect signalling a "DISTANT" signal is provided to indicate the driver about the condition of the stop signal ahead. If the sectional speed is 120 KMPH or above, two "DISTANT" signals shall be provided. In such cases, these signals are called ‘DISTANT’ and ‘INNER DISTANT’ respectively. (b) STOP SIGNALS: Minimum one permissive and one stop signal is sufficient for trains approaching a station. When stop signal is taken 'OFF' it permits the train to enter the station, this is called "HOME" signal of the station. At a station where two stop signals are provided in the approach, the first one shall be called "OUTER' and the next shall be "HOME". In some cases where the distance between the Home signal and the Reception lines of the station is far away, one more stop signal may be provided, as One Home signal will not be sufficient to facilitate the reception. So a stop signal provided between Home and the Reception lines shall be called a "ROUTING HOME". 5.3 SIGNALS FOR DEPARTURE OF TRAINS At the departure end of the station, the stop signals controlling the movement of trains leaving the station are; (a) STARTER SIGNAL: Where the departure of trains is controlled by only one stop signal, it is called Starter Signal and is the Last Stop Signal of the station. If two or more converging lines are there, the Starter shall be placed outside all connections on the line to which it refers. Where advanced starter is also provided, the starter referring to any line is placed so as to protect the facing point or fouling mark and shall not be less than 400m in advance of the Home signal. (b) ADVANCED STARTER: Where departure of trains is controlled by more than one Stop Signal, the Outer most starter signal shall be the Last Stop Signal of the station and is called "Advanced Starter". Unless approved under special instructions an "Advanced Starter" shall be placed outside all connections on the line to which it applies. It shall be placed at not less than 180m in the case of two aspect and 120m in multiple aspect signalling from the outermost point on single line and out side all connection. This distance shall be reckoned from the starter on double line. On special nominated sections where frequent shunting involving main line takes place the "Advanced Starter" signal may be placed at a distance of full train length beyond the trailing point and the track between trailing point and the advance starter shall be track circuited (Ref. C.slip No.2 for para 7.16.6 & 7.27.5 of 1988 SEM). Where an advanced starter is provided, the starter referring to any line shall be placed so as to protect the first facing point or fouling mark; and shall not be less than 400m in advance of Home Signal. Page 21 BASICS OF SIGNAL ENGINEERING DESIGNATION OF SIGNALS (c) INTERMEDIATE/ROUTING STARTER: Intermediate Starter is provided between starter & advanced starter where necessary, and is placed in rear of the point, which it protects. (Refer Figs. 6.2, 6.3, 6.4 and 6.5 of the next chapter) 5.4 We have seen the aspects and indications of an individual signal. The following aspect sequence charts give us the various combinations of signals, their aspect and indications conveyed to the driver of an approaching train. (Using light aspects) (a) Approaching Signals used in 2-Aspect Signalling Warner Outer Home Indication R R R Stop at Outer Signal R G G Enter the station. Stop at Starter of concerned line if 'ON’ G G G Run through via main line all signals ahead are 'OFF' (b) Approaching signals used in MAUQ/MACL Distant Home Indication Y R Stop at Home Signal YY Y Enter on Loop line. Stop at Starter if 'ON’ G Y Enter on main line. Stop at Starter G G Run through via main line (c) Using two Distant Signals in approach (MACL). Distant Inner Distant Home Indication YY Y R Stop at Home YY YY Y Enter on Loop Line. Stop at Starter if 'ON’ G YY Y Enter on Main Line. Stop at Starter G G G Run through via main line 5.5 Aspect sequence chart of Stop signals used for departure of trains (a) Departure signals in 2-aspect signalling Starter Advanced Starter Indication R R Stand in rear of starter G R Shunt upto adv. Starter G G Proceed line is clear (b) Departure signals in M.A Signalling Starter Advanced Starter Indication R R Stand in rear of starter Y R Shunt upto adv. Starter Y/G G Proceed line is clear 5.6 To control the through movement of trains to and from a station, it is sufficient to have reception and despatch signals as explained above. But in some major yards, other special type of signals and indicators are provided, (a) to control short moves within the yard; and (b) to convey certain information to the driver (They are discussed in Chapter.7). IRISET Page 22  REVIEW QUESTIONS Review Questions Subjective Questions 1. Write down aspect control chart of distant signal in double distant territory. 2. Write down advantages of double distant signal. Objective Questions State true OR false 1. When distant signal display green aspect then it indicates run though condition (False/ True) 2. Normal aspect of distant signal in double distance territory is caution. (False/ True) Fill up the blanks 1. If distant signal in single distant territory display proceed aspect then it indicates----- a) Run through on main line b) Run through on loop line c) Train is going to be received on Main line d) all a,b &c 2. If distant signal in double distant territory display proceed aspect then it indicates--- a) Run through on main line b) Run through on loop line c) Train is going to be received on Main line d) all a,b &c *** Page 23 BASICS OF SIGNAL ENGINEERING LOCATION OF SIGNALS CHAPTER 6: LOCATION OF SIGNALS 6.1 Signal must be so located and aligned as to display the best possible view of their aspects to the driver of approaching train and shall avoid as far as possible the possibility of mistaking the aspect of one signal for the aspect of another, or confusion between the lights of running signals and the lights of subsidiary signals or any other lights. Signals should be normally on the left hand side or above the line to which they apply, unless there are special reasons to the contrary. All signal arms must be fixed on the left-hand side of the post. The other important considerations in locating the signals are that they should afford the required sighting distances and it should be possible to work or operate them efficiently, and should not infringe the schedule of dimensions. None of these considerations can be compromised. Signals should be so designed, failure of which shall assume the most restrictive aspect. It shall be noted that the adequate distances prescribed in these rules are minimum they may suitably be increased but not decreased, unless authorised by special instructions. 6.2 LOCATION OF SIGNALS IN 2-ASPECT L.Q.SIGNALLING (a) WARNER SIGNAL: A Warner signal may be placed either (i) On a post by itself with a fixed green light by night 1.5 to 2 metres above it and shall be located not less than. 1200 metres in rear of the first stop signal or Gate Stop Signal, unless otherwise it is permitted by approved special instructions. Or (ii) On the post, 1.5 to 2 metres below the arm of the outer signal. Or (iii) On the post, 1.5 to 2 metres below the last stop signal of a station. When placed below a stop signal the variable light of the stop signal shall take the place of fixed green light of the Warner Signal, and the arrangement shall be such that the Warner cannot be taken 'OFF' while the stop signal above it is 'ON'. The Warner signal must not be capable of being taken 'OFF' for any line other than that over which highest speed is permitted, and it must not be capable of being taken 'OFF, until the levers of all the relevant signals have been pulled. Where it is necessary to provide un-worked Warner Signal, it must be fixed at 'ON' position as shown in Fig 6.2. (b) OUTER SIGNAL: In 2-aspect signalling where outer signal is provided, will be the first stop signal of the station and shall be placed not less than 400 metres in rear of the point upto which the line may be obstructed after the line clear has been given to the station in rear. On single line there should be at least 580 metres between Outer and Home, so as to cater for Block overlap and Signal overlap i.e. (400 + 180m) where advance starter or Shunt Limit Board is provided for shunting facility in the face of an approaching train. (c) HOME SIGNAL: The Home Signal shall be located in rear of all connections, and close to the first set of facing points clear of lock bar, or the fouling mark (if the first point is trailing) so as to protect the adjacent line. If it is found necessary to increase the distance between the signal and the first facing point beyond 180 metres, other arrangements for route holding must be made like lock retaining bar, with successive interlocking or track circuits or SM's route control. (d) ROUTING SIGNAL: A Routing Signal must be placed in rear of the point, which it protects. (e) STARTER SIGNAL: The starter signal shall be placed at not less than 400 metres in advance of the Home Signal. Where a starter signal is provided for each converging line, it shall be so placed as to protect the adjacent running line or lines. Where only one starter is used for two or more converging lines, it shall be placed outside the connections on the line to which it applies. IRISET Page 24  LOCATION OF SIGNALS IN 2-ASPECT L.Q.SIGNALLING (f) INTERMEDIATE STARTER: An Intermediate starter shall be placed in rear of the point or fouling mark to which it protects. (g) ADVANCED STARTER: Unless approved under special instructions, an advance starter shall be placed outside all connections on the line to which it applies. It shall be placed not less than 180 metres from the outermost point on single line. On double line this distance may be reckoned from the starter if this is not adequate enough, may be from the outermost point or fouling point. However in special cases where frequent shunting involving main line takes place, the advance starter may be placed at a distance of full train length beyond the trailing points and the track between starter and advance starter should be track circuited. RECEPTION END DESPATCH END HOME STATION STARTER WARNER ON A POST (FSS) UP DN (LSS) BY IT SELF NBD = 1200M NOT LESS THAN BD = 400M (a) (DN) BRACKETED HOME (DN) STARTERS S.O B.O NBD WARNER BELOW WARNING OUTER (DN) ADV.STR. BOARD (UP) ADV.STR. (UP) 1 KM 400M 180M OUTER WARNER NBD B.O S.O (UP) STARTERS (UP) HOME (b) 400M NBD 1KM BO 400M HOME STN WARNING BOARDS GOODS PASSENGER OUTER WARNER ADVANCE STARTER (c) LSS SO 180M STARTERS (DN) ROUTING SIGNALS STN WARNING BOARDS (DN) (DN) GOODS PASSENGER OUTER HOMES WARNER UP MAIN DN SO 180M 1FP 400M 1KM BO 400M M E NBD HO R DN NE STARTERS AR INTERMEDIATE W S) (UP) ED LS R( SO STARTERS FIX.ST (UP) V M )A D M 0 180 DN (UP BO 40 CH (d) AN 1KM BR UP M 400 NB D Fig. 6.2 DESIGNATION AND LOCATION OF FIXED SIGNALS IN 2-ASPECT L.Q SIGNALLING Page 25 BASICS OF SIGNAL ENGINEERING LOCATION OF SIGNALS 6.3 LOCATION OF SIGNALS IN MAUQ SIGNALLING (a) DISTANT SIGNAL: On single line or double line, the distant signal shall be placed at an adequate distance i.e. Normal breaking distance in rear of the first stop signal of the station or gate stop signal, which shall not be less than 1 km. (b) HOME SIGNAL: The Home signal is the first stop signal of the station normally placed at Normal breaking distance in rear of next stop signal and 180m in rear of the point upto which the line may be obstructed, after the line clear has been given to the station in rear. To obtain maximum operational facility on single line, the Home signal shall be placed at not less than 300m i.e. BO + SO (180m + 120m) in rear of the first facing point if the facility of shunting in the face of an approaching train is desired, so that BO is available between the Home and the opposite advance starter/SLB. Route holding is achieved by providing Lock Retaining bar (LRB) or track circuit or SM's control (See Fig 6.3 a) On double line the Home Signal may be located at a distance of BO (180m) in rear of the facing point or Block section Limit Board (if first point in the approach is trailing or no point). Where two or more lines diverge the signals shall be fixed on bracketed post, or gantry. The signal which refers to main line shall be at higher level than of the loop lines (see 6.3 b) (c) ROUTING SIGNAL: A routing signal must be placed just in rear of the points to which it protects. Generally they are used in junction stations (d) STARTER SIGNAL: Starter signals are usually placed in rear of the facing point or fouling mark of the converging lines such that they should protect the adjacent running line or lines. (e) INTERMEDIATE STARTER: It shall be placed in rear of the point to which it protects. They are generally used at Junction stations to inform the driver of the train that to which direction he is being dispatched (f) ADVANCED STARTER: The advanced starter shall be placed outside all connections on the line to which it applies, and shall not be less than 120 metres from the outermost point on single line. On double line this distance may be reckoned from the starter. However, if this distance is not adequate for working of trains may be reckoned from the outermost point or fouling mark and in special cases up to a distance of full train length beyond the outermost point where frequent shunting is involving the main line. In such cases the track between the starter and advanced starter shall be track circuited IRISET Page 26  STATION SECTION BLOCK SECTION BLOCK SECTION 1.4 Km HOMES NBD CSR 120m 180m 1 Km STARTERS S.O B.O NBD WARNING ADVANCE BOARD DISTANT STARTER LRB UP DN LRB ADVANCE WARNING DISTANT BOARD STARTER 1 Km 180m 120m STARTERS NBD B.O S.O 1.4 Km HOMES NBD STATION LIMITS (a) SINGLE LINE Page 27 BLOCK SECTION STATION SECTION 1.4 Km NBD BLOCK SECTION 1 Km 180m 120m BD B.O S.O LRB BSLB 120m S.O 1 Km BLOCK SECTION BD STATION SECTION 180m 1.4 Km B.O NBD Fig: 6.3 DESIGNATION AND LOCATION OF FIXED SIGNALS IN MAUQ SIGNALLING (b) DOUBLE LINE BLOCK SECTION BASICS OF SIGNAL ENGINEERING LOCATION OF SIGNALS IN MAUQ SIGNALLING LOCATION OF SIGNALS 6.4 LOCATION OF SIGNALS IN (MLQ) MODIFIED LOWER QUADRANT SIGNALLING Modified lower quadrant signalling shall be provided only under special instruction issued by the Railway Board. Nowadays it is not usually adopted. Where such signalling is permitted the requirement of signals and their locations shall be as follows: (a) DISTANT SIGNAL: On single line or double line, the distant signal shall be placed at an adequate distance in rear of the first stop signal which shall not be less than l km. (b) WARNER SIGNAL: It shall be placed on the same post at 1.5 to 2 metres below the main Home Signal. (c) HOME SIGNAL: The Home Signal shall be placed at not less than 180m in rear of the point up to which the line may be obstructed after the line clear has been given to the station in rear. (d) STARTER SIGNAL: It shall be placed on each converging line as to protect the adjacent line or lines (e) ADVANCED STARTER: Placed outside all connections and not less than 120m from the outermost point. If this distance is increased, the track between starter and advance starter should be track circuited. HOME DISTANT WARNER BELOW MAIN HOME ADV.STARTER NBD B.O S.O STARTERS 1Km 180m 120m FIG. 6.4 DESIGNATION AND LOCATIONS OF MLQ SIGNALS 6.5 LOCATION OF SIGNALS IN COLOUR LIGHT SIGNALLING The requirement of signals and their locations in stations equipped with colour light signalling is same as it is for semaphore signalling, whether 2-Aspect or Multiple Aspect. However when colour light signalling is to be provided it is preferable to go for multiple aspect, because it is convenient and advantageous. In the case of semaphore signalling the physical appearance of arm for permissive signal and stop signal is different. Whereas in colour light, the signals look alike, to distinguish a permissive signal from a stop signal a 'P' marker is provided on the post of a colour light Distant Signal. So that the driver need not stop and can pass this signal when it is found blank after seeing the 'P' marker. Similarly providing separate Home signals on a bracketed post for each diverging line, a common colour light stop signal with route indicator is used to indicate the driver as to which route the line is set for him. Route indicator is provided only when the colour light signal is kept common for more than one route for diverging lines and not provided for straight line and when it is for one line. For example starter signals whether on loop line or main line are not provided with route indicator since they are for only one line ahead (see Fig. 6.5). IRISET Page 28  300 m 120m 180m 1 Km STARTERS S.O B.O NBD P DISTANT HOME UP DN P ADV. STARTERS HOME DISTANT 1 Km 180m 120m 300m NBD B.O S.O (a) SINGLE LINE Page 29 1 Km 180m STARTER NBD B.O 120m S.O ADV.STARTER P DISTANT HOME BSLB STARTERS P ADV.STARTER 120m HOME DISTANT S.O 180m 1 Km B.O NBD Fig: 6.5 DESIGNATION AND LOCATION SIGNALS IN MACL (b) DOUBLE LINE BASICS OF SIGNAL ENGINEERING LOCATION OF SIGNALS IN COLOUR LIGHT SIGNALLING LOCATION OF SIGNALS Review questions Subjective Questions 1. Draw a four line class B station with multi aspects colour signal on Double line section with a siding taken out from common loop line. Provide all necessary signals & boards, distances of signals, station limit, station section, block section& also demarcate all possible overlaps of UP home signal. 2. Draw a three-line class B station with UQ multi aspects signal on single line section with a siding taken out from one loop line. Provide all necessary signals & boards, distances of signals, station limit, station section, block section& also demarcate all possible overlaps of UP home signal. Objective Questions State true OR false 1. First stop signal on signal line station normally shall be placed at distance of 400 Mt plus 180 Mt from outer most point. (False/ True) 2. First stop signal on double station line normally shall be placed at distance of 400 Mt plus 180 Mt from outer most point. (False/ True) 3. The starter signal shall be placed at not less than 400 metres in advance of the Home Signal and is usually placed in rear of the facing point or fouling ma of the converging lines such that they should protect the adjacent running line or lines. (False/ True) 4. Location of distant signal and warner signal on independent post is same. (False/ True) 5. Location of advance starter in LQ and UQ signal on single line and double line may be reckoned starter signal. (False/ True) *** IRISET Page 30  SUBSIDIARY SIGNALS CHAPTER 7: SUBSIDIARY SIGNALS, REPEATERS, INDICATORS, MARKERS & BACK LIGHTS 7.1 In the previous chapters we have seen the signals authorising the drivers to enter the station from a block section by the use of Reception Signals; and enter the block section from the station by the use of Departure Signals. These signals were, therefore, being used for "reception and despatch of running trains. As per definition a "Running train" is a train which has started under an authority to proceed and has not completed its journey whereas "a train" is an engine with or without vehicles attached or self propelled vehicle with or without a trailer which cannot be readily lifted off the track. The signals, which control the movement of trains within the station section, are to be differentiated and convey different indication to the driver. These signals are (a) Shunt signals and (b) Calling on Signals and are called "SUBSIDIARY SIGNALS". 7.2 SUBSIDIARY SIGNALS In addition to the reception and despatch of train from and to a station some other movements of trains are required such as transfer of vehicles from one line to another, attaching and despatching of vehicles to and from a train, to marshall a train so that vehicles meant for the same destination are always in one line, etc. Such movements differ from regular train moves in which the speeds are low as the movements are confined to a small area and the line on which the movement is to be done may invariably be occupied by vehicles and as such the driver has to exercise more caution. A running signal taken 'OFF' signifies that the line on which the movement is to take place is clear whereas a shunt signal if taken 'OFF' may authorise the driver to go past the signal at slow speed irrespective of whether the line is occupied or not. These movements are also required to be controlled and 'NOT LEFT' to the discretion of the driver. These movements can be carried out by the use of "Hand Signals" exhibited by authorised persons to carry out the shunting. Where these movements are frequent and regular then the use of separate signals called "Shunt Signals" have to be fixed. Naturally the shunt signals are to be different