CH 18.pdf

Chapter 18: Block Instruments, BPAC & IBS Working Section 1: Block Instruments General Requirements 18.1.1 General (a) All block instruments shall be of robust construction and approved type only. (b) On sections where AC voltages are induced due to power line parallelism, suitable block instruments with appropriate protective measures shall be provided as per Section. (c) Block instruments shall normally be worked on physical conductors. Where required, block instruments may also be worked on Radio/Optical Fibre Cable with appropriate security features. (d) Lightning Discharger: All Block instruments shall be provided with lightning discharger to approved specification. Where a return line wire is used, lightning discharger must be installed on both wires. (e) Prevention of Irregular Operations: There shall not be any opening giving access to the interior of the instrument through which it is possible to operate the mechanism by any irregular means. (f) Locking and Sealing Facilities: Facilities shall be provided for locking and sealing the Block instruments. The doors of the Block instruments giving access to the internal mechanism shall be provided with a double lock, the key of one of which shall be in the custody of the Station Master on Duty and the key of the other will be with the technician signal in charge of the maintenance of Block Instruments. It shall not be possible to open the door of the Block Instruments without the co-operation of both the agencies. (g) Prevention of Unauthorized Operation: A lock or other device shall be provided to enable the Station Master on duty to prevent unauthorized manipulation of the instrument during his absence. (h) Isolation of Telephone Circuit: Telephone instrument shall be provided in conjunction with block instruments. It is desirable that the condenser or other means provided for isolating the telephone circuit from the instrument circuit is located within the instrument or in such a way as to be inaccessible for outside interference. (i) Bell Push: A Bell push button or a bell plunger shall be provided on the instrument for exchange of bell codes. (j) An isolated power supply (battery in standalone mode or DC-DC Converter with isolated output) shall be used for line circuit for each block instrument. This power supply shall only feed the block instrument and not any other circuits. The power supply housing shall be locked and sealed if provided in the SM’s Room. Note: Where Integrated Power supplies (IPS) are used for Block working, isolated DC-DC convertor Modules shall be used for each Block separately. (k) Tokenless Block Instruments worked on physical conductors shall be worked on metallic return circuits. Chapter 18: Block Instruments, BPAC & IBS Working Page 356 of 530 (l) If section is installed with Embedded type Block working i.e. Block working built into Electronic Interlocking, VDU kept in ASM room shall have Block Indication display in both the VDU with hot standby feature. Display Descriptions shall be followed as per Drawing No. RDSO/S/32019. 18.1.2 Special Requirements of Single Line Token Block Instruments (a) Fixed Indications: The instruments shall be provided with visual indication clearly giving the following indications: (i) When the instruments are normal and there is no train in the block section, "Line Closed" at both the stations. (ii) When Line Clear for a train to leave the Block station in rear has been given, "Train Coming From" at the receiving station. (iii) When Line Clear for a train to leave a Block station has been received from the Block station ahead, "Train Going To" at the sending station. (b) Current Indicator: An indicator, indicating the polarity of current, shall be provided to indicate incoming and outgoing line currents. (c) Operation: "Train going to" and "Train Coming From" - The instruments shall be such that the cooperation of the Station Master at the other end of the section shall be necessary. Even with the co-operation of the Station Master at the other end, the Station Master has to go through one or more definite moving operations on the instrument in addition to working of bell plunger. (i) Before he can grant Line Clear to the Station Master at the other end of the section to release a token, or (ii) Before he can obtain Line Clear and extract a token. (d) "Line Closed": Both the instruments shall be restored to normal before a further operation of setting the instrument to "Train Going To"/"Train Coming From" can be carried out. It shall not be possible for the instruments at either end of the section to be restored to normal without the cooperative features indicated in para 18.1.2(c). (e) Operation of "Line Clear" Receiving and Granting Mechanism: It shall not be possible for the mechanism which permits a "Line Clear" to be received and that which permits a "Line Clear" to be granted to be in operation at the same time. (f) The instrument that is set to "Train Going To" for initiating a train movement shall be the first one to be restored to "Line Closed" on complete arrival of the train at the receiving station. (g) Extraction of Token: It shall be possible to extract one token only when the instrument has been set to "Train Going To". It shall not be possible to change the "Train Going To" condition until the token has been inserted in one of the instruments of the Block section. Chapter 18: Block Instruments, BPAC & IBS Working Page 357 of 530 (h) Token instruments shall be so installed that a token of one block section cannot be placed in the instrument of an adjacent section and preferably such that if the token is over carried, it cannot be placed in an instrument at the next station. (i) The Tokens of each section shall be engraved with the code name of the stations at both ends of the block section and with a serial number. 18.1.3 Special Requirements of Single Line Tokenless Block Instruments (a) Fixed Indications: In addition to the fixed indications specified in para 18.1.2(a) the instrument shall be provided with means to indicate "Train on Line" at both the sending and receiving stations when a train has entered the block section. (b) Immunity from Extraneous Currents: Single Line Token less block instruments shall work on coded impulse/frequency modulated current system so as to be immune from the effects of extraneous currents. (c) "Train going to" and "Train Coming From": The instrument shall be such that even with the cooperation of the Station Master at the other end of the section, the Station Master has to go through one or more definite moving operations on the instrument in addition to the working of bell plunger. (i) Before he sets his instrument to "Train Coming From". (ii) Before he sets his instrument to "Train Going To". (d) "Train on Line": Means shall be provided to ensure that the instruments are set to "Train on Line" automatically by the entry of the train into the block section and maintained in that position until the train has cleared the block section. This indication shall be in addition to the "Train Going To" or "Train Coming From" indications of the handle. (e) "Line Closed": Both the instruments shall be restored to normal before a further operation of setting the instrument to "Train Going To"/"Train Coming From" can be carried out. It shall not be possible for the instruments at either end of the section to be restored to normal without the cooperative features enumerated in para 18.1.3(c). 18.1.4 Operations: Push Button Tokenless Block Instruments (a) "Train going to" and "Train Coming From": The co-operation of the Station Master at the other end of the section may be dispensed with. The instrument shall be such that a button in addition to the bell button shall be operated for "Train Going To" position. (b) "Train on Line": Means shall be provided to ensure that the instruments are set to "Train on Line" automatically by the entry of the train into the block section and maintained in that position until the train has cleared the block section. This indication shall be in addition to the "Train Going To" or "Train Coming From" indications. Chapter 18: Block Instruments, BPAC & IBS Working Page 358 of 530 (c) Line Closed: Both the instruments shall be restored to normal before a further operation of setting the instrument to "Train Going To"/"Train Coming From" can be carried out. The instrument shall be such that a button in addition to the bell button shall be operated by the receiving station for setting both the instruments to the "Line Closed" condition. This feature can be dispensed with where an automatic device of closing the Block section is provided. (d) Operation of "Line Clear" receiving and granting mechanism - It shall not be possible for the mechanism which permits a "Line Clear" to be received and that which permits a "Line Clear" to be granted to be in operation at the same time. (e) Token less block instruments shall be provided with (i) Audible indicators to warn the receiving station.  When the train enters the block section at the sending station.  When the train has passed the Home Signal at the receiving station. (ii) Shunting key suitably interlocked with the Block instrument for use as an authority for shunting behind the Last Stop Signal and up to the opposing First Stop Signal. 18.1.5 Special Requirements of Double Line Block Instruments (a) Indicators for Up and Down Lines: The Instruments shall be provided with Visual indicators separately for Up and Down Lines to show the following three conditions: (i) Line Closed (ii) Line Clear (iii) Train On Line (b) Current Indicator: The indicators provided as per para 18.1.5(a) may also serve as the current indicators. (c) Operation before Granting or Receiving Line Clear: The instrument shall be such that the Station Master has to go through one or more definite moving operations on the instrument besides working the bell or plunger before he can grant Line Clear. (d) Audible Indicator: Where required, the instruments may be provided with audible indicators (i) to warn the receiving station when the train has passed the Home Signal, and (ii) to warn the sending station when the train has passed the Last Stop Signal. Chapter 18: Block Instruments, BPAC & IBS Working Page 359 of 530 18.1.6 Non-Co-operative type Instruments The requirements indicated in para 18.1.5 will apply to these instruments. In addition, the following shall be provided in these instruments. (a) Automatic "Train On Line": Means to ensure the instruments are set to "Train On Line" position automatically by the entry of the train into the block section and maintained in that position until the train has passed the Home Signal at the receiving station and the instrument set to "Line Closed" condition. (b) Audible Indicator: Audible Indicator to warn the receiving station when the train enters the block section at the sending station. (c) Shunting Keys: Two Shunting keys, one for each line, suitably interlocked with the block instruments for use as an authority for shunting in the block section. Train Detection for Proving Block Section to be Clear: On sections where use of track circuits/Axle counters for proving the block section to be clear is to be introduced, the following equipment shall be provided: (a) Track circuits or Axle Counters extending from the Last Stop Signal of the block station at one end of the block section to the other end First Stop Signal of the block section. (b) An indicator in each block station to show whether the block section is occupied or not. (c) A control to ensure that the Last Stop Signal of the block station in rear is automatically replaced to 'ON' by the passage of a train and maintained in that position until the train has cleared the block section. (d) A control to ensure that the First Stop Signal is automatically replaced to 'ON' by the passage of the train. (e) On single line, a control to ensure that the opposing Last Stop Signals of the Block section cannot be taken 'OFF' at one and the same time. Section 2: Special Requirements of Block Working in RE Area 18.2.1 In 25 KV electrified line only following type of block instrument shall be used: (a) Single Line: (i) Single Line Token instrument (Neal's) (ii) Single Line Token less Block Instrument Handle type (Daido) (iii) Block working with Axle Counter (iv) Block Proving by Axle Counter (v) Block working directly from EI Note: (i) Neal's Token instrument shall be progressively phased out. (ii) Push button type block instrument may be used on non-electrified section taking off from electrified section, if length of parallelism does not exceed 1.5 km. Chapter 18: Block Instruments, BPAC & IBS Working Page 360 of 530 (b) Double Line: (i) Double Line Block Instrument (SGE) (ii) Block working with Axle Counter (iii) Block Proving by Axle Counter (iv) Block working directly from EI Note: If any other block instrument is to be used, prior approval of Railway Board shall be obtained. 18.2.2 Media (a) Block instruments may use special PVC insulated quads in the aluminum sheathed cable/4 or 6 quad jelly filled telecommunication cable or other suitable communication means, like OFC and radio, for their working. (b) When quad cable is used for the working of block instruments, Block Telephone and Block Bell circuits shall be worked through a transformer utilizing the two pairs of block quad. The Block circuits shall be worked on the phantom pair or by other suitable means. (c) When OFC, Radio or other communication means are used for block working, Universal Fail Safe Block Interface (UFSBI) of approved design shall be used. UFSBI shall be installed in relay room and the connected block panel shall be provided in ASM room. In case the distance between UFSBI and block instrument is more than 500 meters, block filter and block bell and telephone shall be inserted in cable pairs connecting them. 18.2.3 Others (a) Protective Devices of approved type consisting of two chokes connected in series with a four terminal condenser connected across the junction between two chokes and earth shall be used. A surge arrestor of suitable type shall also be provided across the condenser to absorb surges under faulty conditions. The arrangement is illustrated in Drg. No. 18-D4. (b) The Block Bell shall be worked through Block Bell equipment of approved type. (c) Separate line battery or DC-DC converter shall be used for each block instrument. This battery shall feed only the block instruments and not any other circuit. Note: Two different earths shall be provided separately for SPD and Block. However, the protective earth for SPDs of all Block equipments should be connected to common ring earth of Indoor Signalling system. Chapter 18: Block Instruments, BPAC & IBS Working Page 361 of 530 18.2.4 Single Line Token Block Instrument in RE Area (a) Where earth return is used, the rest contact of the instrument shall be substituted by the contacts of a slow release relay. The arrangement shall be such that the relay is energized during the operation of plunger but is dropped only after the condenser has discharged to a safe limit. The circuit details are illustrated in Drg. No. 18-D5. (b) Whenever stray DC is present in the earth, metallic return is provided for block circuit. Metallic return should be used with a modified filter circuit eliminating the condenser. The chokes and surge arrestors shall be retained and shunt resistors shall be provided across the Galvo (150 ohms) and Polarised Relay (77 ohms). The resistors shall be of substantial rating so that they do not get open circuited. The circuit details are illustrated in Drg. No. 18-D6. In this case, slow to release relay is not required. 18.2.5 Double Line Block Instrument in RE Area (a) IRS type Block Instrument with Block filter shall be used for Double Line section electrified with 25 KV AC. The circuit details are illustrated in Drg. No. 18-D7. (b) The voltage of the Battery shall be sufficient to ensure not less than 18 ma and not more than 25 mA current through the polarized relay. Needle coil resistance shall be modified to obtain this level of current. Section 3: Installation of Block Instruments 18.3.1 General Fixture (a) All block instruments shall be of approved type only. (b) The Table or other fixture on which instruments are placed must be substantial and the Instruments are securely fixed there on. (c) Turn-table arrangement may be provided for fixing the Token and Handle type instruments to enable easier maintenance but the plate on which the instrument turns shall be securely fixed to the table. (d) Block Instruments, Distinction of: Where two or more block instruments are located in the same room, they shall be fitted with bell units/ bell buzzers of distinctive tones. Note: Painting of Block Instruments shall be in accordance with the painting scheme in Annexure: 18-A1. Chapter 18: Block Instruments, BPAC & IBS Working Page 362 of 530 18.3.2 Transmission Media and Wiring (a) Line Wires: The line wires from the point where the lines of two adjacent block sections meet to the terminating point on or near the building shall either be insulated or be so erected as to be not less than 150 mm from any other wire. The provision of insulated wires should be preferred. The insulated line wires must be terminated on pot-head insulators. The line wires must not be easily accessible. Alternatively, a cable, suitably protected, may be used, but a separate cable should be provided for each instrument circuit. The insulated line wires must be led in sloping upward to the building, otherwise a drip loop should be provided. (b) Leading in Wires: The wires leading into the building from the terminating point shall be adequately separated from the wires of other circuits and shall be single, braided or metal sheathed, run in one length from the pot- head insulator to the test panel. Alternatively, a cable, suitably protected, may be used, but a separate cable should be provided for each block instrument circuit. (c) Indoor Wires: Indoor wires must be run in troughing or other suitable form of trunking which provides protection from interference and separation from the wires of any other circuit. (d) Radio/Optical Fibre Cable: Where radio channel or optical fibre cable is used in lieu of line wires, approved type block interface shall be provided. Note: All wires or cables shall be in accordance with the Indian Railway Standard Specification or other approved specification. 18.3.3 Protective Measures against Power Line Parallelism (a) Lightning Dischargers shall not be located in the Block Instrument but installed separately and shall be the demarcating point for test purposes. (b) It shall be ensured that induced voltage due to power line parallelism does not exceed 150 V and the short circuit fault current does not exceed 430 V as prescribed by CCITT. (c) If the induced voltage goes beyond these limits, overhead block circuit shall be transferred to an underground telecom PET quad cable/OFC/Radio, so as to bring the induced voltage within the permissible limits. (d) Since the immunity of PR relay is only up to 10 V, block filters shall be used in all block instruments using this relay where this limit is exceeded. (e) Block filters shall be used with Handle type Block instruments using frequency coded signal. (f) Use of single line push button token less block instruments is permitted in sections where length of parallelism does not exceed 1.5 km, so as to ensure that the DC coding used in these block instruments is not distorted. Chapter 18: Block Instruments, BPAC & IBS Working Page 363 of 530 18.3.4 Earthing (a) A separate earth shall be provided for each instrument. The earth shall be of an approved type and should be buried at a depth of not less than1.5 meters and at a distance not less than 2.5 meters from any other earth. The resistance of the earth should not be more than 10 ohms. Note: Separate earth is applicable for only those equipments which work on earth return. (This does not apply to block instruments which work on metallic return) Also the protective earth for SPDs of block instruments to be connected to common ring earth of Indoor Signalling system. (b) The length of the Earth wire shall be as short as possible and cross section of the wire not smaller than the size of the line wire and in any case shall not be smaller than 4 mm dia. The earth wire shall not have a sharp bend or spiral. Earth wire should be adequately protected from mechanical injury and be efficiently connected to the earth. All connections to the earth shall be well soldered. Section 4: Installation of Single Line Token Instruments 18.4.1 (a) The Token instruments shall be so installed that the token of one section cannot be placed in any other instrument at that station. It is also desirable that the installation be such that if the token is over carried, it cannot be placed in any instrument at the next station. (b) Consecutive block sections shall be provided with tokens of configurations A, B & C. Following block sections shall also be provided with similar configuration in the same order. Where a junction station falls in between or new crossing station is opened, tokens with special configuration (D&E) shall be provided. (c) Block Instruments must be mounted level (spirit level may be used) so that tokens will not get into any particular race in case of ball Token instrument and the token will not tilt in case of tablet type Token instrument. 18.4.2 Tests to be Conducted After Installation and Before Commissioning (a) Check that correct polarities are connected to the instruments at both the ends. (b) Check that all mechanical parts are free to move without undue friction and that there is no jamming of moving parts. (c) Check that the commutator does not change unless the token gets into the races in the case of Ball Token instruments and slides down the rail beyond the tablet receiver in the case of Tablet Token instrument. (d) Check that the insulation of electrical components and internal wiring of the block instrument is proper and free from leakage from the instrument body/earth. Note: RDSO Booklet STS/E/BTI/IMI may be referred to for detailed instructions regarding installation & testing. Chapter 18: Block Instruments, BPAC & IBS Working Page 364 of 530 Section 5: Installation of Single Line Tokenless Block Instrument 18.5.1 (a) The instruments shall be mounted level. The instruments shall be so placed as to have an easy access and space for their maintenance. (b) Before installation, the instrument shall be checked for the following: (i) Free from mechanical damage, corrosion. All nuts and bolts shall be secure and complete. (ii) The Front Panel shall be free from splitting, twisting or warping in case of Push Button type instruments. (iii) The seal of all the relays and counters shall be intact. (iv) Sealing. (c) All the external connections to the block instrument shall be removed and insulation resistance measured between individual insulated circuits and Earth. The minimum value between each individual insulated circuit and Earth shall not be less than 10 mega ohms. (d) Block release shall be by operation of two track circuits sequentially. 18.5.2 Testing of Single Line Tokenless Block Instruments (a) Check that the Last Stop Signal at the sending station cannot be taken 'OFF' until the receiving station instrument is set to "Train Coming From" condition and the sending station instrument is set to "Train Going To" condition. (b) Check that the Line Clear can be granted only when reception signals and the Last Stop Signal are proved at 'ON'. (c) Check that the Last Stop Signal is replaced to 'ON' by the entry of a train into the block section and the same is maintained in the 'ON' position until the train has cleared the block section and the instruments are brought back to the 'Line Closed' condition and fresh "Line Clear" is obtained. (d) Check that the opposing Last Stop Signals of the block section cannot be taken "OFF" at one and the same time. (e) Check that the circuit for proving the arrival of a train is directional. (f) Check that the shunting key can be taken out only when the instruments are in "Line Closed" condition or "Train Going To" condition. Chapter 18: Block Instruments, BPAC & IBS Working Page 365 of 530 Section 6: Installation of Double Line Block Instruments 18.6.1 (a) Quick acting relays shall not be used for stick circuits of the block instrument. Two immunized plug-in type 'Q' series relays connected in tandem or one 'Q' series slow to pick up AC immunized relay shall only be used. The total pick up time of relays used shall not be less than 300 msec. DC 3-position polarized line relay of approved type shall only be used in the line circuit for block working. (b) Block release shall be by the operation of two track circuits sequentially. 18.6.2 Tests to be Conducted at the Time of Installation (a) Check that the commutator handle is locked first before the "Train on Line" indication appears on the indicator when the handle is turned from "Line Clear" to "Train on Line" position. (b) Check that the Block Clearance Relay picks up only after the commutator is turned to "Train on Line" position. (c) Check that the Last Stop Signal cannot be taken 'OFF' when the commutator is in other than "Line Clear" position. (d) Check that the Last Stop Signal is automatically replaced to 'ON' when the train enters the block section and continues to remain in the 'ON' position until the train has arrived at the receiving station and a fresh “Line Clear” is obtained. (e) Check that when the commutator is turned from "Line Closed" position to "Train On Line" position, the commutator is free for return to “Line Closed” position. Section 7: Maintenance of Token Instruments - General 18.7.1 Register of Block Instruments The Senior Section Engineer (Signal) shall maintain a register containing the following information: (a) The type of instrument, its serial number, location, and name of manufacturer. (b) Date of installation. (c) Date of last overhaul. (d) Particulars of all tokens working in each block section and particulars of tokens either removed or lost irrecoverably during the course of working and of those introduced as replacement. 18.7.2 Census of Tokens: Each Sectional JE/SSE (Signal) shall take a census of the tokens working in various block sections at least once in six months and shall keep their record in the register of Block Instruments. He should also record this information in the Signal History Book at every station and keep it up to date in this respect. Chapter 18: Block Instruments, BPAC & IBS Working Page 366 of 530 18.7.3 Damaged Tokens (a) Tokens, which are cracked or deformed or have worn to a size smaller than the normal size or are damaged in any other way and are liable to jam in an instrument and cause a failure shall be removed, broken up and returned to Stores. Advice of tokens that have been removed shall be given to all concerned. (b) Token so removed shall be replaced with another token of the same number and all concerned advised. 18.7.4 Lost Tokens (a) When a token has been lost and cannot be found after a thorough search, a joint certificate to that effect shall be given to the Senior Divisional/ Divisional Signal and Telecommunication Engineer by the supervisors of the Signal and Telecommunication Department and the Operating Department. On receipt of the certificate, a joint circular shall be issued by the Senior Divisional/ Divisional Signal and Telecommunication Engineer and the Sr.Divisional Operating Manager giving full particulars and cancelling the lost token for the information of the staff. The particulars of the lost token shall be published in the Railway's Gazette. (b) Particulars of lost tokens on Card No. S&T/TL, as per Annexure: 18-A2 shall be conspicuously exhibited near the relevant instrument for the information of the Operating Staff. (c) If a lost token is not found for six months, it shall be replaced with a token of next higher number in continuation of the series in use on the section. The lost token, if found subsequently, shall be broken and returned to stores. 18.7.5 Balancing of Tokens (a) Technicians shall, whenever necessary, transfer tokens from the instrument in which they have accumulated to the instrument at the other end of the section. Each Technician in charge of single line token instruments shall be provided with a "Token Balance Book" consisting of Form No. S&T/TB, as per Annexure: 18-A3, serially numbered. Each book before issue shall be endorsed by Senior Section Engineer (Signal) as under: "Page _______ to _______ checked and found correct". (b) Technicians shall fill up portions 'A' and 'B' of Token Balance Book form and take the signatures of – The Station Master of the Station from where tokens have been extracted to verify that token numbers as mentioned were extracted from the instrument with his permission; and the receiving Station Master to verify that token numbers mentioned in the book have been correctly deposited in the relevant instrument. (c) An entry in the "Train Signal Register" shall be made to this effect. (d) Station Masters shall have instructions to advise the Technician (signal) by wire/control message as soon as the balance of tokens in their token balance register falls to "Six". Chapter 18: Block Instruments, BPAC & IBS Working Page 367 of 530 (e) Extracting of/replenishment of tokens in Token instruments shall be done when the instruments are in the "Line Closed" position. (f) Token pouches shall be kept in proper repair by the Traffic Department and damaged pouches shall not be allowed to be used. Note: Also refer to para No. 18.9.1. 18.7.6 Responsibility of the Operating Staff (a) Staff operating the instruments is responsible for the safe working of the instruments, which is dependent on the correct use of the code of bell signals and the correct operation of the instruments being carried out in proper sequence. (b) Importance of Bell Signals: The provision of telephones does not do away with the necessity for use of authorised code of bell signals. Section 8: Maintenance of Block Instruments & their Ancillary Apparatus - General Instructions 18.8.1 (a) Technician shall ensure by a fortnightly check that (b) Locks: Electrical or Mechanical Locks are in a condition that they are not liable to be forced. (c) Indicators: Indicators operate fully and return to the normal position correctly when released. (d) Contacts: All contacts are clean and free from pitting, if surfaces are pitted, they shall be cleaned with chamois leather and refurbished. (e) All springs are in good condition and kept properly adjusted. (f) Relay Armatures: Relay armatures are free and return to their normal position when no current is flowing. (g) Track Circuits: Instructions as laid down in Chapter 17 of SEM shall be adhered to. (h) External Wiring: All wiring is in good condition and free from joints. Joints, wherever necessary, are properly soldered and insulated. (i) Terminal Screws: All terminal screws, lock nuts and locking screws are kept tight and split pins opened. (j) Batteries: All batteries are kept clean, terminals tight and free from dirt or corrosion and maintained in accordance with instructions in Chapter 16 of SEM. (k) Lightning Protector: Lightning and power protective devices and earth connections are effective and in good condition. Chapter 18: Block Instruments, BPAC & IBS Working Page 368 of 530 (l) Block Instrument Telephone: Block instrument telephone, its flexible cord and the condenser or other means provided for isolating the telephone from the Block instrument circuit are in good condition. The isolation is such that there is no direct path for the current to flow from one circuit to the other. (m) Receiver diaphragms are not buckled and are at the correct distance from the pole pieces. (n) Receiver ear piece fits correctly and is screwed tight. (o) When a pair of block instruments of a block section falls in different contiguous Railway/Division, both instruments and their associated equipment shall be maintained by one agency. 18.8.2 Overhauling of Block Instruments: Periodical overhauling interval shall not exceed ten years for Single Line Token Block Instruments and seven years for Double Line Block Instruments and Handle type Single Line Token less Block instruments. Push Button Token less Block Instruments, UFSBI Block panel, and Embedded block working in Electronic Interlocking etc. do not require overhauling. The associated polarised relay shall also be overhauled along with the Block instrument. 18.8.3 Block Earths (a) Block earths and their connections shall be examined at intervals of not more than one month by the Section Engineer (Signal) and at intervals of three months by the Senior Section Engineer (Signal). (b) Block earths shall be tested for resistance at intervals of not more than 12 months by the Section Engineer (Signal) or Senior Section Engineer (Signal) in accordance with Annexure: 19-A3. Where the resistance exceeds 10 ohms, action shall be taken to reduce the resistance by providing additional earths in parallel. (c) In AC electrified areas, two different Earths shall be provided for Discharger and Block Earth. (d) The four Terminal Condenser used in filter shall be connected in such a way that the DC circuit is completed through the plate or foil of the condensers. It shall be ensured that any break in the foil or Earth connection, which might affect the efficiency of the filter, puts the circuit itself out of use. Chapter 18: Block Instruments, BPAC & IBS Working Page 369 of 530 Section 9: Maintenance of Single Line Block - Instructions 18.9.1 Single Line Token Instruments (a) Care shall be taken to see that the safety catch provided near the spring clutch shaft is in position and functioning properly and free to move about the fulcrum without any friction. (b) Token indicator shall be checked to see if it is free to move. The pin shall be oiled once a fortnight with axle oil medium grade to IS: 1628. Effectiveness of 'No token' lock shall be checked. It shall not be possible to take handle to “Train Going To” position when token indicator shows Red. (c) Care shall be taken to see that "Train going to" and "Train Coming From" locks rocker arm is free to move about its fulcrum pin. The locks shall be about 1 mm above the rack; if not, the locks shall be changed. The edge of the lock shall be square. (d) It shall be ensured that all parts of the instrument, which undergo wear and tear, are replaced at the time of overhauling. (e) The locking Pawl shall be checked to ensure that it is correctly shaped, square ended and the width is 9.5 mm. (f) Care shall be taken to see that in the case of Tablet instrument, the tablet holding arm release lever is working satisfactorily and the tablet can be released only after full rotation and release of the instrument handle in the Train Going To" position. (g) It shall be checked that the notches in the rack are correctly shaped and square. Note: (i) RDSO Booklet No. STS/E/BTl/IMI may be referred to for detailed instructions regarding maintenance of Token instruments. (ii) Stipulation as given in section 7 of this chapter may be referred. 18.9.2 Single Line Tokenless Instruments – Push Button Type: The tests enumerated in para 18.5.2 shall be carried out during routine maintenance. 18.9.3 Double Line Block Instruments – SGE Type: Locking assembly shall be replaced during each overhauling irrespective of its condition. It shall also be ensured that all parts of the instrument which undergo wear and tear are replaced at the time of overhauling as per approved instructions. Note: (1) Tests enumerated for Double Line Block Instruments in para 18.6.2 shall also be carried out during routine inspection. (2) Maintenance Schedule for Block Instruments are given in Annexure: 18-MS1 in Appendix I. At stations having heavy traffic the Railways may prescribe more frequent inspections, if considered necessary. Chapter 18: Block Instruments, BPAC & IBS Working Page 370 of 530 Section 10: Maintenance of Block Proving by Axle Counter 18.10.1 Block Proving by Axle Counter using UFSBI Block Panel (a) Various parameters of Axle Counter track equipment and UFSBI shall be maintained within permissible values as per the instructions issued from time to time and as per the OEM manuals. (b) It shall be ensured that various signal levels at prescribed points of electronic equipment are within permissible limits as per laid down instructions. Section 11: Maintenance of Embedded type Block working 18.11.1 Block working built into Electronic Interlocking (a) Maintenance and parameter of Embedded type Block working shall be maintained as per maintenance schedule of Electronic Interlocking and Video Display Unit (VDU) maintenance schedule issued from OEM maintenance manual. (b) It shall also be ensured that all equipment connected with EI related with Block working shall work as per laid down instructions Section 12: Intermediate Block Signalling (IBS) 18.12.1 General Requirements (a) IBS is an arrangement made for increasing the section capacity by splitting of a relatively a long block section into two portions namely rear section and advance section by placement of IBS at the point of near bifurcation, subject to other considerations, such as presence of steeper gradients on approach of the IBS, neutral section, visibility of signals etc. If required, up & down IBS may be staggered to suit the local condition. (b) The rear section i.e. "station controlled intermediate block section" starts from LSS of the rear station and ends at IBS including 400 meters block overlap in that direction. (c) Advance section i.e. "block controlled Intermediate Block section “starts from IBS and ends at home signal of advance station including block overlap in that direction. (d) Track sections both in Rear section i.e. "station controlled intermediate block section" & Advance sections i.e. “block controlled Intermediate Block section” are monitored either by Axle Counter or by Track circuit. (e) Train entry into rear section i.e. "station controlled intermediate block section" is controlled by LSS of rear station in that direction. (f) Train entry into advance section i.e. “block controlled Intermediate Block section” is controlled by IBS in that direction. Chapter 18: Block Instruments, BPAC & IBS Working Page 371 of 530 (g) A Signal Post Telephone (SPT) or any approved type communication shall be provided at the IBS post for communication with the station in the rear. (h) IBS system needs distant and inner distant signal where applicable for pre warning of IBS. (i) IBS works like Class C station & IB Distant signals are to be provided to match with the section signaling. (j) IBS block overlap of 400 m shall be separately monitored. (k) Where axle counters are provided, resetting arrangements are also to be provided. (l) Provision must be there to indicate that a train has passed IBS at “On” Position/blank. (m) IBS system needs panel with various indications and push buttons at each block station pertaining to direction of traffic. (n) IB Signal shall be provided with a marker consisting of a white coloured disc with letter 'IB' in black. (o) Control of IBS lies with the SM of station in rear. 18.12.2 Resetting Operations: There are two types of resetting operations which requires co-operation of the other end Station Master. (a) When a train passes IBS at “On” position/blank. (b) When Axle Counter fails. 18.12.3 IBS system will permit only one train in the entire block section, when a train passes IBS at “On” position or axle counter is not clear even after the passage of the train beyond the axle counter section. Procedure to be followed by the Loco Pilot to pass IBS at “On” position/blank as per GR 3.75: (a) When phone communication is available between IBS and rear station, the loco pilot shall stop his train in rear of the IBS and contact the SM of block station in rear on SPT, then pass the defective IBS, if authorized by SM. (b) When phone communication is not available between IBS and the rear station, the loco pilot after waiting for 5 minutes can go beyond IBS at a speed not more than 15 kmph which should be reduced to 8 kmph in case of inadequate visibility like fog, night conditions etc. The loco pilot should proceed at restricted speed till he reaches advance station. Monitoring is required through indication for IBS blank. Chapter 18: Block Instruments, BPAC & IBS Working Page 372 of 530 18.12.4 IBS in Double Line: (a) IBS should be interlocked with any of the approved means of block working for Double line. (b) IBS shall not be taken off for Train unless line clear has been obtained from Block Station in advance. (c) DLBIs/Block Panel of BPAC etc. pertaining to the monitoring of advance section are placed at the rear and advance stations. 18.12.5 IBS in Single Line: (a) Provision shall be there, to establish the direction of traffic for IBS in single line. (b) First direction of traffic shall be established and then line clear shall be obtained from the Block station in advance as per the established direction of traffic. Only after establishing the direction of traffic the train movement in the station controlled intermediate block section shall be permitted. (c) IBS shall not be taken off unless the line clear has been obtained from Block Station in advance and direction of traffic is established. (d) IBS should be interlocked with any of the approved means of block working for Single line. ------------------------------------------------ ooooo ----------------------------------------------- General Note: (1) IB Signal shall be located in such a way, to split the block section into near halves subject to other criteria. IB Signal shall not be provided in a Block section with steep falling gradients, unless the brake power is adequate to enable the trains being stopped at IB signal. (2) One of the methods of providing IB signals using OFC (optical fiber cable) and Multi Section Digital Axle Counter (MSDAC) is given at Annexure: 18-A4 as an example for guidance only. Note: This Chapter has under mentioned Annexures S.No. Annexure No. Description 1 18-A1 Painting Scheme - Block Signalling Equipment 2 18-A2 Tokens Lost/Tablets Lost 3 18-A3 Token Balance Book 4 18-A4 Intermediate Block Signalling (using OFC, MSDAC) Chapter 18: Block Instruments, BPAC & IBS Working Page 373 of 530 Note: This chapter has under mentioned Maintenance Schedule in Appendix-I S.No. Annexure No. Description 1 18-MS1 Maintenance Schedule of Block Instruments (Single Line, Double Line, Push Button) 2 18-MS2 Maintenance Schedule of Block Instrument – Double Line (Lock & Block) 3 18-MS3 Maintenance Schedule of Tokenless Block Instrument - Single Line (Push Button type) 4 18-MS4 Maintenance Schedule of Analog Block Axle Counter Systems (BPAC): CEL MAKE 5 18-MS5 Maintenance Schedule of Tokenless Block Instrument - Single Line (Handle Type) 6 18-MS6 Maintenance Schedule of Universal Fail-Safe Block Interface (UFSBI) Note: This chapter has under mentioned Drawings in Appendix-II S.No. Drawing No. Description 1 18-D1 IB Hut Layout Plan (Double line/Single line) 2 18-D2 IB Signalling with MSDAC & OFC (Double line) - (Sheets-2) 3 18-D3 IB Signalling with MSDAC & OFC (Single line) - (Sheets-2) 4 18-D4 Filter Unit for Block Circuits 5 18-D5 Protective devices for AC Electrified Area of Neale’s ‘A’ Type Token Instrument - Earth Return 6 18-D6 Protective devices for AC Electrified Area of Neale’s ‘A’ Type Token Instrument - Metallic Return 7 18-D7 Double line Block working with Protective Device for AC Electrified Area. Chapter 18: Block Instruments, BPAC & IBS Working Page 374 of 530 Para No. 18.3.1 Annexure: 18-A1 Painting Scheme – Block Signalling Equipment 1. Single Line Ball Token/Tablet Token Block Instruments (a) Body … Grey Enamel Operating Handle, Bell except … (b) Gong, Station Master’s Control Black Enamel Lock 2. Single Line Tokenless Block Instrument (A) Handle Type (B) Push Button Type (a) Body … Grey Enamel (b) Operating Handle, if any … White (c) Base … Black Enamel 3. Double Line Block Instruments (a) Wood Work … Spirit Polish (b) Metal Casing … Green Enamel 4. Token Delivery nets … White 5. Line clear pick up apparatus (a) Post … White (b) Fittings … Black Chapter 18: Block Instruments, BPAC & IBS working Page 375 of 530 Para No. 18.7.4(b) Annexure: 18-A2 Tokens Lost/Tablets Lost ………….. RAILWAY SIGNAL & TELECOMMUNICATION DEPARTMENT BLOCK SECTION………………………. Division …………………………………. Station ……………………………… Type of Block Instrument ………………………………………………………………… Serial No……………………………………………. Date of Installation …………………………………….. Serial No. of Signature and Serial No. of Date Lost New Token Date Inserted remarks of Token Lost used SSE/JE (Signal) Chapter 18: Block Instruments, BPAC & IBS working Page 376 of 530 Para No. 18.7.5(a) Annexure: 18-A3 Form S&T/TB Token Balance Book …………………… Railway Signal & Telecommunication Dept. Division ………………………………. Block Section……………………… Name of Maintainer……………………… Designation…………………………….. Section …………………………….. Quantity of Token in use on Section …………….. Portion A Portion B Tokens taken from ……………………… Tokens taken from ……………………… (Name of Station) (Name of Station) each token taken Serial Number of Serial Number of Station Master Station Master Tokens taken Tokens taken Date & Time Date & Time Signature of Signature of Signature of Signature of Total No. of Total No. of Maintainer Maintainer each token brought brought away away 1 2 3 4 5 6 7 8 9 10 Chapter 18: Block Instruments, BPAC & IBS working Page 377 of 530 Annexure-18-A4 Intermediate Block Signalling (using OFC, MSDAC) For Intermediate Block Section, the block section is divided into two sections of approximately equal length where two trains can be accommodated simultaneously in each direction of traffic. For Intermediate Block signaling, various schemes are in use in Indian Railways based on different types of vehicle detection devices and mechanism used to drive the remote IB Signals. Presently, the typical IB signaling schemes in existence are (i) Conventional IB with copper cable (ii) IB with Quad and copper cable (iii) IB with EI and OCs (iv) IB with UFSBI. In all these above schemes, Analog axle counters/Single Section Digital Axle Counters/Dc Track Circuits are used for track vacancy detection and to drive the signals at IB, to read the status back and for resetting mechanism, various schemes have been used. In addition to above, Multi Section Digital Axle Counters (MSDACs), with dual detection in distributed architecture may also be used for track detection as well as exchange of signaling information and resetting. Reliability of conventional IB signaling may face two problems. (i) The SSDACs are provided without duplication, which may lead to intermittent failures, thus making the system less available. (ii) Signaling and Power cables provided along the IB block section are terminated in location boxes with at least 2 RE cuts between Station and IB requiring power supplies in them. These location boxes are in inaccessible locations, which are difficult for regular maintenance and also for attending to failures. With a number of location boxes in the circuit, the probability of failure also proportionally increases. Hence, the scheme with dual MSDAC for detection of track vacancy over OFC and IO-EXBs for exchange of signaling information between two locations, duly minimising signalling & quad cables, with no RE cut sections in between gives reliable working. I. Introduction: The Intermediate block signalling consists of two major components. A) Provision of axle counters for track vacancy detection in rear as well as advance sections B) Exchange of signalling and reset information between IB and stations. In the scheme presented here, dual detection with redundancy at each level including communication media is adopted to achieve higher availability. Track vacancy detection has been achieved through Multi Section digital axle counters and exchange of signalling information is done by using Multiplexing facilities of MSDAC. Chapter 18: Block Instruments, BPAC& IBS Working Page 378 of 530 II. Description of the Scheme A. Typical layout of the scheme: The Intermediate Block Section between Two Stations is reffered for easy understanding. The typical layout of the placement of different DPs and Signals is as follows: Fig 1. Typical Layout of IBS A Relay hut of size 12 m x 5 m is provided to cater for RBG room at IB location. The IB home Signals are typically planned in such a manner that, the UP and DOWN IB signals are near to Relay hut and as such both signals are driven from the hut including the corresponding distant signals. The nomenclature of DPs in DOWN direction is DN-DP1A, DN- DP1B, DN-DP2A, DN-DP2B, DN-DP3A, DN-DP3B, DN-DP4A, DN-DP4B. Similar nomenclature has been adopted for UP direction also. B. Provision of MSDACs for track vacancy detection and defining the boundaries of track section and Supervisory Track Sections: Chapter 18: Block Instruments, BPAC& IBS Working Page 379 of 530 DN-MAIN DN-REDUNDANT FROM TO TRACK SECTION FROM TO TRACK SECTION DNDP1-A DNDP3-A DN-AC-A DNDP1-B DNDP3-B DN-AC-B DNDP2-A DNDP3-A 7 AC-A DNDP2-B DNDP3-B 7 AC-B DNDP2-A DNDP4-A DN-BPAC-A DNDP2-B DNDP4-B DN-BPAC-B DNDP1-A DNDP4-A DN-SPT-A DNDP1-B DNDP4-B DN-SPT-B Fig 2. Boundaries of Track Section Dual detection has been provided with redundancy for all other equipment as well as communication media. The Typical IB section consists of Three track sections in each direction. (i) AS track section, which starts from the foot of LSS and ends at 400 meters ahead of IB home signal (DN-AC) (ii) IB track section, from the foot of the IB home signal to 400 meters ahead of the signal (7 AC) (iii) BPAC section, from foot of the IB home signal to 180 meters ahead of the home signal of the ahead station for proving block overlap (DN-BPAC). A supervisory track section (DN- SPT) covers all these three track sections, which is used for second level of reset as explained in later sections. Chapter 18: Block Instruments, BPAC& IBS Working Page 380 of 530 Dual detection: Fig3. Dual Detection There are few instances where it is observed single detection (whether SSDAC or MSDAC) is prone to failures irrespective of precautions taken. (i) Whenever a loaded rake movement is there over the coil portion, due to light weight of the guard brake, there exists a considerable probability of the wheel jumping over the coil causing a miscount and thereby counting mismatch and failure of axle counter. (ii) When there is a long haul movement or due to any unavoidable reasons, if the wheel traces a to and fro movement over the portion of coil, the system goes into hang state which requires rebooting of the same. This is prevalently observed not only in SSDAC but also in MSDAC. (iii) Unintended count due to food foil: It has been an experience in few cases, where the Aluminum food foil which runs along the track gets struck and attaches to the Rx Coil, which causes unintended out count or in count leading to failure of Axle counter. In all above cases, if dual detection is provided with staggering of coils, such failures may be avoided through Automatic reset feature. Redundancy of other components of MSDAC: In order to avoid other equipment failures such as Power supply card, communication card, mother board as well as relay driver card and relay failures, all are duplicated including communication media. Chapter 18: Block Instruments, BPAC& IBS Working Page 381 of 530 Fig 4. Typical equipment Block diagram As shown in Fig.4, the redundancy at equipment level is achieved as follows: (i) At wheel sensor level, dual detection is provided with two DPs on either rail in each direction of traffic. (ii) Two separate TLJBs are provided with IP65 protection for termination of each DP. Fig 5. Termination box for DP (iii) The 6 quad cable from Relay hut to location box is duplicated and provided in two different paths to achieve path redundancy. Chapter 18: Block Instruments, BPAC& IBS Working Page 382 of 530 (iv) Each Coil/DP is connected to an Advanced Evaluation Board (AEB) through a surge protection device, for processing of data received from coil. (v) Two evaluators (EVs), Main and Redundant (M&R) are provided in IB location as well as adjacent stations. The main DPs of UP and DOWN direction are connected to EV(M) and redundant(R) DPs of UP and DOWN direction are connected to EV(R). The evaluated information is shared to Relay Driver card and COM-AdC. The COM- AdCs at IB as well as adjacent locations are on a common network through ethernet ports and in turn through dedicated OFC, via an unmanaged ethernet switch as shown in Fig.4. The COM-AdCs of both M & R EVs are hot linked and any failure of one of the board does not hamper the track detection. (vi) There are two ethernet switches available for shared communication among the MSDACs at all the three locations. One ethernet switch works on dedicated fibres (Tx &Rx). Another ethernet switch works on a pair of quad cable. Alternatively, the second one can also be provided over redundant fibre. Fig 6. Ethernet Switch (vii) The Vital Relays (ACPRs) of each track section are picked up at the Entry end of track section (either in IB location or station). The status of vital relays exchanged between two location through IO-EXBs depending on the need. C. Exchange of signaling information between two locations The IB signal relay status has to be repeated from rear station to IB location. Similarly the status of IB signal as well as other vital and non vital indications have to be exchanged between IB location and Stations. In order to achieve this, the IO-EXBs are used in either location, with each pair exchanging 3 vital I/Os between them. The vital mode is typically termed as quad mode in which 3 I/Os of vital information can be exchanged, where as the non vital mode is termed as single mode, where 12 I/Os can be exchanged between two locations with a pair of IO-EXBs. The typical Information required to be exchanged between two locations is as follows. Chapter 18: Block Instruments, BPAC& IBS Working Page 383 of 530 AXR2-C1 BP-EXB4, EXB3-105 NW-IBS (DN) INPUT - QUAD MODE OUTPUT-QUAD MODE INPUT FUNCTION OUTPUT FUNCTION INPUT 1A OUTPUT 1A INPUT 1B OUTPUT 1B 7 DR-B 7 DECR-B INPUT 1C OUTPUT 1C INPUT 1D OUTPUT 1D INPUT 2A OUTPUT 2A INPUT 2B OUTPUT 2B SPARE 7 RECR-B INPUT 2C OUTPUT 2C INPUT 2D OUTPUT 2D INPUT 3A OUTPUT 3A INPUT 3B OUTPUT 3B SPARE SPARE INPUT 3C OUTPUT 3C INPUT 3D OUTPUT 3D AXR2-C3 BP-EXB4, EXB2-104 NW-WADI INPUT - QUAD MODE OUTPUT-QUAD MODE INPUT FUNCTION OUTPUT FUNCTION INPUT 1A OUTPUT 1A INPUT 1B OUTPUT 1B UP-CRR-B UP-ACPR-INDC-B INPUT 1C OUTPUT 1C INPUT 1D OUTPUT 1D INPUT 2A OUTPUT 2A INPUT 2B OUTPUT 2B UP-CO-PR-B DN-CRR-B INPUT 2C OUTPUT 2C INPUT 2D OUTPUT 2D INPUT 3A OUTPUT 3A INPUT 3B OUTPUT 3B DN-ACPR-INDC-B DN-CO-PR-B INPUT 3C OUTPUT 3C INPUT 3D OUTPUT 3D AXR2-C1 BP-EXB4, EXB4-106 IBS-NW (DN) INPUT - SINGLE MODE OUTPUT-SINGLE MODE INPUT FUNCTION OUTPUT FUNCTION INPUT 1A SPARE OUTPUT 1A 7D HECR-B INPUT 1B SPARE OUTPUT 1B 7D DECR-B INPUT 1C SPARE OUTPUT 1C 7D HHECR-B INPUT 1D SPARE OUTPUT 1D 7 ID HECR-B INPUT 2A SPARE OUTPUT 2A 7 ID DECR-B INPUT 2B SPARE OUTPUT 2B SPARE INPUT 2C SPARE OUTPUT 2C SPARE INPUT 2D SPARE OUTPUT 2D SPARE INPUT 3A SPARE OUTPUT 3A SPARE INPUT 3B SPARE OUTPUT 3B SPARE INPUT 3C SPARE OUTPUT 3C SPARE INPUT 3D SPARE OUTPUT 3D SPARE Fig 7. Vital and Non-Vital I/O between IB and station Chapter 18: Block Instruments, BPAC& IBS Working Page 384 of 530 D. Reset feautures of MSDAC The reset arrangement is given at three levels using Track Sections and Supervisory Track Sections, two of which are automatic reset arrangements and one is manual reset. (i) L -I : Automatic reset with redundant track section: Once the train has cleared both the track sections, and any one of the track sections is in failure state, the track section, which is in clear condition will reset the one in failed condition. The track section, which is under reset is kept in preparatory mode and the clear track section information is used to take off the signal. (ii) L -II : Automatic reset with Supervisory track section: When a supervisory track section is clear, all the track sections falling completely within the jurisdiction of that supervisory track section can be assumed to be clear. If any track section fails and it’s corresponding supervisory track section is clear, it will automatically reset the failed track section. In case of automatic resetting with supervisory track section, the reset track sections will be kept under preparatory mode, and the corresponding signal will continue to be in ‘ON’ aspect, until a train with low speed enters and exits the track section with equal count at the boundaries of track section. As shown in Fig.2, DN-SPT is a supervisory track section which covers all the track sections of IB in DOWN direction. If any one of the track sections fail, within the entire IB, DN-SPT resets that track section and keeps in preparatory mode. (iii) L -III : Manual Reset with Line verification: In case of failure of Level-1 and Level-2 reset, manual resetting has to be carried out, which resets all the failed track sections in the section under consideration. One reset box at train sending station along with its corresponding Line verification(LV) box at other station is used to manually reset all the track sections between both the stations of a particular direction of movement. This reset can be done only when Station Masters of both the stations have ascertained that all the track sections between the stations are clear of trains in that particular direction. This will reset and set all the failed track sections in preparatory mode. The clearance of train in each section with balancing of count will make the track section clear and bring to its normal mode of working. E. Power Supply Arrangement The IB location is provided with a Mini IPS, for which the input supply of 230 V AC is from UP AT and DN AT. The necessary power supplies for MSDAC are derived from the Mini IPS. MSDAC works on a voltage range of 19-72 V DC. Hence 24 V DC supply with suitable current capacity from Mini IPS serves the purpose. In stations, the necessary power supplies are derived from the Major IPS. F. Cable requirement Signaling Cable: In the stations, Home & Advance starter signals are directly fed from the EI/Relay room with standard signaling cable, with aspect repeating relays at signal locations. IB Signals at IB location are directly fed using a 12x1.5 Sq.mm signaling cable from Relay Hut, without any repeater relay at site, as the distance is not more than 200 meters. Chapter 18: Block Instruments, BPAC& IBS Working Page 385 of 530 Quad Cable: MSDAC evaluator to each DP requires 1 quad of 4 conductors. A separate 6 quad cable is used for each DP of dual detection (main + Stand-by) from the nearest Half location box provided for Signal cable termination at signal location. From IB Hut to Half location box one 6 quad each is used for UP & DN directions. The media between Station to IB location is duplicated by providing 6 Quad cable in addition to OFC cable. The OFC as well as Quad ethernet switches work in hot stand-by mode with seamless change over to each other without disturbing the communication working. Disclaimer: (1) The scheme given above, was adopted in 2018-19 in Anakapalle - Bayyavaram section in Vijayawada divn/SCRly, is only for Technical information of signal Engineers and does not indicate endorsement of any particular make of MSDAC. (2) Scheme will have to be suitably modified as per Technical requirements/Facilities in particular make of MSDAC & other equipments being used. ________________________________________________________________________ Encl: Drawings are given at 18-D1, 18-D2, 18-D3 in Appendix -II Chapter 18: Block Instruments, BPAC& IBS Working Page 386 of 530

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