Block Sigg System

BLOCK SIGNALING SYSTEM "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. (GR 1.02.(10)) ”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. (GR 1.02.(6)) “Intermediate Block Signalling" means an arrangement of signalling on a double line in which a long block section is split into two portions each constituting a separate block section by providing an Intermediate Block Post. (GR 1.02.(32)) "Last Stop Signal" means the fixed stop signal of a station controlling the entry of trains into the next block section. (GR 1.02.(34)) '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. (GR 1.02.(37)) 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 -(GR 1.03.(2)) Class 'A' stations - where Line Clear may not be given for a train unless the line on which it is intended to receive the train is clear for at least 400 metres beyond the Home Signal, or upto the Starter. Class 'B' stations - where Line Clear may be given for a train before the line has been cleared for the reception of the train within the station section Class 'C' stations - block huts, where Line Clear may not be given for a train unless the whole of the last preceding train has passed complete at least 400 meters beyond the Home Signal and is continuing journey. This will also include an Intermediate Block Post.

(3)

Non-block stations or Class 'D' stations are stopping places which are situated between two consecutive Block stations and do not form the boundary of any block

SYSTEMS OF WORKING 1. All trains working between stations shall be worked on one or other of the following systems, namely. (i) (ii) (iii) (iv) (v) (vi)

Absolute Block System Automatic Block System Following Trains System Pilot Guard System Train Staff and Ticket System One train only system

ESSENTIALS OF ABSOLUTE BLOCK SYSTEM: Where trains are worked on the Absolute Block System:

1) (a)No train shall be allowed to leave a block station unless Line Clear has been received from the Block Station in advance, and (b)On Double Lines, such line clear shall not be given unless the line is clear, not only up to the first stop signal at the block station at which such Line Clear is given but also for an adequate distance beyond it; (c)On Single Line, such Line Clear shall not be given unless the line is clear of trains running in the same direction, not only up to the first stop signal at the Block Station at which such Line Clear is given, but also for an adequate distance beyond it, and is clear of trains running in the direction towards the block station to which such Line Clear is given. 2.) Unless otherwise directed by approved special instructions, the adequate distance referred to in clause (b) and (c) of sub-rule (1) shall not be less than (a)400 meters in case of two aspect lower quadrant signaling or two aspect color light signaling and (b) 180 meters in case of multiple aspects signaling or modified lower quadrant signaling.

AUTOMATIC BLOCK WORKING Introduction : Automatic Block Working is a system of train working in which movement of the trains is controlled by the automatic stop signals. These signals are operated automatically by the passage of trains into through and out of the automatic signalling sections. The following are the essentials of Automatic Block System. Where trains are worked on Automatic Block System: (a) the line is track circuited throughout its length and divided into a series of automatic signalling sections each of which is governed by an Automatic Stop Signal. (b) the movement of trains is controlled by stop signals which are operated automatically by the passage of trains past the signals. (c) No Automatic Signal assumes 'OFF' unless the line is clear not only upto the stop signal ahead, but an adequate distance beyond it. 6.1 Adequate Distance or Overlap : The adequate distance referred to above, which may also be termed 'overlap' shall not be less than 120 metres unless otherwise directed by approved special instructions.

SINGLE LINE NEALE’S BALL & TABLET TOKEN INSTRUMENT. The use of token Block Instruments is permitted for controlling trains on a single line section. The object of providing such instruments is to prevent more than one train being in a block section at a time, and when the block section is clear, to admit one train into the section from either of the two ends, thus, guaranteeing absolute safety in the running of trains at all times, maintaining space interval between two trains. To achieve this a pair of Token Block Instruments, each containing a stipulated number of tokens (bearing serial number and code initials of the stations to which they apply), electrically interconnected are provided one at each end of the Block Section. The instruments are designed to have conscious co-operation of the two Station Masters at either end of the Block Section for electrically releasing a token from any one of them. This token is handed over to the driver of a train as an Authority to Proceed i.e., to leave the Block Station and enter the Block Section. Mechanism is provided to ensure that only one token can be released if none is extracted already from either instrument, and if once a token has been extracted, a second token cannot be extracted either from the same or the other instrument till such time the token already extracted is restored to either of them and the instrument set to normal and a fresh sequence of operations gone through.

DOUBLE LINE BLOCK INSTRUMENTS. There are 3 types of Double Line Block Instruments:1) SGE Type (Byculla Make) 2) IRS Type (HWH Make) 3) SGE Modified Type (PTJ Make) The main differences among them are:i) Contact arrangement ii) Housing of components like polarised relay, Bell Assembly, Bell Relay, Telephone etc. iii) Design of TOL Lock (Mechanical stick or Electrical Stick). Though there are differences in the design aspect, all the three types are approved for use in RE and Non-RE sections. . This is a three wire three position double line block instrument. The indications for the up and down directions are controlled by one wire each and the bell and telephone are worked by the third wire, earth being employed for return circuit. In cases where interference from extraneous currents is likely to occur, a metallic return may be provided for the block lines leaving the bell communication to be worked by earth return. The instrument consists of two needle indicators placed one above the other. A commutator, with a bell-plunger threaded through its middle is provided below the bottom indicator. The single stroke bell for exchanging code of bell signals, is provided as a separate unit.

Fig : FRONT VIEW OF SGE DOUBLE LINE BLOCK INSTRUMENT

In this double line block instrument, the indicator which is operated by the commutator is placed above to the latter, and the commutator is operated only by the advanced station operator when he receives a train. Therefore, the bottom indicator of the instrument which is nearest to the commutator refers trains coming from the adjacent station to which the instrument is connected and the top indicator refers to trains going to the adjacent station of the same Block section. This is a simple block instrument wherein the advanced station operator has to operate the commutator of his instrument during the three stages of receiving a train i.e., 1) while granting 'Line Clear' (ii) when the train has entered the block section at the rear station and (iii) when the instruments are again normalised after the complete rrival of that train. By providing an electric lock on the commutator when it is in the "Train on Line" position and by adding other controls in the form of external circuits advantages of Lock & Block working are obtained electrically. The indications of the Bottom indicator correspond to the positions of the commutator.

Installation of Block Signaling equipment on 25KV A.C. traction Area Block instrument with certain protective devices can be used for AC Traction for double line sections. Neale's type of single line block instruments can also be used with certain modifications and protective devices. Push button type Single line Tokenless Block Instruments may be used on Non-Electrified Section taking off from Electrified section if the length of parallelism does not exceed 1.5 km.:a) A filter of an approved design shall be installed between the single or double line block instrument and the line wire. The general arrangement for these filters are shown in Fig. It is essential that the line and block instrument terminals of the filters are never interchanged. The filter is a low pass filter consisting of series choke coils S1 and S2 in each line and the shunt condenser CI. The condensers adopted are 4-terminal condensers to prove the continuity of the conductors forming the condenser. Also two gaseous type lightning arrestors with a flash voltage of 150 volts are provided on the line side for high voltage protection. Two different Earths shall be provided for Discharger and Block. Separate Line Battery shall be used for each Block Instrument. This battery shall feed only the Block Instruments and not any other circuit. b) SCHEMATIC DIAGRAM OF BLOCK FILTER UNIT

HANDLE TYPE TOKENLESS BLOCK INSTRUMENT FOR SINGLE LINE IRS SPECIFICATION NO. IRS-S-98-2001. The instruments are designed to work either on 1800 Hz or 2700 Hz Carrier frequencies. The Modulating frequencies are 85 Hz and 65 Hz. The codes used in the instrument are:1)

1800 Hz or 2700 Hz modulated by 85 Hz with DC +ve - To permit operation of block handle from Line Closed to TCF, TCF to Line Closed and TGT to Line Closed.

2)

1800 Hz or 2700 Hz modulated by 65 Hz with DC +ve - To permit operation of Block handle from Line Closed to TGT.

3)

1800 Hz or 2700 Hz modulated by 65 Hz. - To set the other end instrument to "Train on Line"

4)

DC - VE for exchanging bell code signals.

Note: In the above 2

(i) DC +ve refers to line battery +ve connected to line 1 and -ve to line (ii) DC -ve refers to Line battery -ve connected to Line 1 and +ve to Line 2.

PUSH BUTTON TOKEN LESS BLOCK INSTRUMENT IRS SPECIFICATION S 32/66 1.1 INTRODUCTION: The main purpose of introducing Token less Block working is to reduce the block operating time. This could be achieved up to a limited extent only in the instruments of the handle type. The co-operation of the other station at the time of obtaining line clear even though it is established that the section is clear or at the time of closing the Block Section after the arrival of the train is still needed in the handle type of instruments. To obtain the full advantage of Token less block working, a Token less block instruments of the push button type have been evolved & the above drawbacks are eliminated. 1.2 System: Token less Block Instrument of the push button type consists basically of a set of push buttons provided on a control panel and relays provided in a cabinet. For a block section one instrument is installed at each end of the block section and the instrument are connected with two line wires. In this instrument there is no mechanical interlocking and the interlocking is purely by relays. Merely by operating push buttons on the control panel, various operations can be done. . 1.3 To set the instrument to "Train Going To" condition push buttons BCB (Bell Code Button) and TGB (Train Going to Button) are pressed simultaneously at the train sending station. This operation transmits the "Train Coming From" code to the instrument at the other end and if the conditions for granting of "Line Clear" are satisfied, sets the instrument to "Train Coming From" condition. After the instrument at the receiving end is set to TCF, “TGT code” is automatically generated and transmitted back to set the instrument at the despatching end to "Train Going To" condition. 1.3.1 Similarly, when the train arrives at the receiving end, operation of push buttons BCB and LCB (Line Closed Button) simultaneously at the receiving end results in transmission of the “Line Closed Code” to the other end instrument and setting that instrument to Line Closed Condition. The instrument at the despatching end after setting to Line Closed generates Line Closed Code automatically and transmits “Line Closed Code” to set the Train receiving Instruments to Line Closed Condition. 1.3.2

Three step polar impulse coding is employed in these instruments as follows: -

TCF Code For setting the instrument to TCF + TGT Code -doTGT + TOL Code -doTOL Line Closed Code -doto normal + + either from TGT or from TCF position. Or on cancellation of line clear both in normal or on push back operation. For transmission of bell signal positive current is sent on line 1 (L1) and -ve on line 2(L2) 1. A relay cabinet housing all relays, and 2. A dash board called 'Control Panel' containing push buttons, indicators, bell, telephone, etc.

INTERMEDIATE BLOCK SIGNALING

1 Intermediate Block Signaling (IBS) is an arrangement of Signaling on Double Line Section which is substituted to 'C' Class Station, which otherwise will be required (manned by Operating Staff) for the purpose of splitting of long Double Line Section into two portions. To avoid the expenditure on the Block Instruments, Station buildings and recurring cost of Operating Staff, IB Signaling either with continuous track circuiting between the Last Stop Signal of the Station in rear up to the overlap of IB Signal or with an axle counter with the entrance and exit point located at the LSS and at the overlap of IB signal respectively can be provided. The Station Master of the Block Station in rear controls the IB signal. On a number of Railways, such IB Signaling installations are working satisfactorily and are giving good improvement in the running especially of Goods Trains since IBS permits two trains to be present in the Block Section at a time as against one train with absolute Block System and this considerably minimizes detention for second train when a slow earlier train has already entered the Block Section. 2 For each direction, one IB Signal at the place where the section is divided into two and a distant signal at minimum 1 KM from IB Signal shall be provided. A typical arrangement of IB-Signaling is indicated in diagram No.1. This shows the IB Signaling with Axle Counters. It is also possible to have IBS with two track circuits, one from LSS to IB signal and another from IB-Signal up to the overlap of 400 meters. To the extent possible Up IB Signal and down IB-Signal has to be kept close so that both can be controlled from the same IB-Equipment room located close to the signals. This room will accommodate the relays controlling the IB signals and IB Distant Signals, Lamp Proving relays, track proving relays etc., and AC Power Supply for signals as well as 12V or 24V D.C. battery power supply with its own battery charger required for repeater of IB relays at the corresponding signal cabin of Station ‘A’ (Sending Station) and Station 'B'. While locating IB signal, it should preferably be located in such a way that the travel time for the train will be equal for both the halves of IB-Section so that optimum headway can be maintained between the trains at maximum possible speed. However, consideration like gradient at approach of IB signal and existence of Neutral Section, visibility for signals etc., have also to be considered while locating the IB-signal. If required up and down IB signals may be staggered to suit the local conditions. Accordingly the distant signals are also to be located.

BLOCK WORKING THROUGH AXLE COUNTER 1 In the conventional double line block instrument all the operations are done by the receiving station master and this could result in detention to trains at the sending end in case of non-availability / pre-occupation of the receiving station Master. Moreover complete arrival of the train by checking up the LV board/Tail lamp is done manually by the receiving Station Master and in case if any failure to adhere to this procedure strictly there is a possibility of Block being closed even if parting had occurred in the mid-section and the train had arrived incomplete. Some accidents had taken place by way of mid-section collision due to closure of block section with some vehicles of the train still remaining in the block section. Axle Counter was thought of for use in block working to overcome the twin problems of (1) dependence of human agency to verify the complete arrival of the train and (2) cut down delays associated with the granting of line clear in conventional double line block working. 2 Basically the scheme attempts to replace the normal double line block instrument with a block operating panel, associated relays and an axle counter at stations on either end of the block section on double line. The operating panel is used for obtaining line clear and cancellation. Etc. and axle counter is used to automatically verify that the section from LSS up to the block overlap beyond the first stop signal at receiving end is clear of any train before the line clear can be obtained from the station and also to automatically verify that the train which had left the dispatching station had arrived complete at the receiving station before the block section can be once again closed (which incidentally is automatically done by the system without any need for intervention by the operator). The line clear can be obtained by the sending Station Master without the co-operation of the receiving Station Master (But if receiving station does not want to give line clear he has to take out the line clear blocking key) and on arrival of the complete train at receiving station by taking off home signal, the section is closed automatically. This way the operating procedure has been designed so as to minimise the time involved in obtaining line clear and also closing the block section as compared to the conventional double line block instrument. With proper arrangements for approach warning at LC gates, the system can also be used with slight modification at a later date as an open block system/automatic block system. Axle Counter Block Working is possible on Double line & Single line system. In Single line one axle counter or double line two axle counters are used. The system consists of relay logic circuit of combined converter units at both ends and relay status data is exchanged by using safe digital multiplexing which employs FSK coded signal. BLOCK MULTIPLEXER: It is a equipment, which repeats the Block working relay information from one station to the other in a failsafe manner. This is achieved on a single line by using suitable multiplexing techniques. This relay information is digitally coded and sent as safety coded frequency shift keying signals. The frequencies used are 1300 Hz. and 2100 Hz. The buad rate is 1200 BPS.