80 Questions
In Hot-standby mode, what happens to track vacancy detection in case of failure of one DP?
Track vacancy detection is not affected
What is the purpose of providing redundancy in Track circuits/Axle Counters in the Automatic Section?
To improve the reliability and availability of the system
What is the purpose of Supervisory track sections?
To automatically reset track sections
What is the purpose of the resetting facility in individual track sections?
To reset the track section in case of equipment failure
How many track sections are covered by a single Supervisory track section?
Two
What connects the main DPS of UP and DOWN direction?
EV(M) and EV(R)
What is the purpose of providing a Track Indicator in Automatic Signalling on Single Line?
To indicate whether the block section is occupied or clear
What is the purpose of media diversity in Axle Counters?
To improve the reliability of the system
What is the purpose of COM-AdC board in MSDACs?
To communicate with adjacent EVs
What happens if one COM-AdC board fails?
No impact, the system continues to function
What is the purpose of the 'A' marker on an Automatic Stop Signal?
To identify the signal number
What is the purpose of the ethernet switch in Fig. 4?
To transfer evaluated information to OFC
What is the purpose of the enamelled yellow disc with letters 'G' in black on a Semi-Automatic Stop Signal?
To indicate that the signal is interlocked with a level-crossing
What is the purpose of the 'A' marker light on a Semi-Automatic Stop Signal interlocked with a level-crossing?
To indicate that the gates are closed and locked against road traffic
Where are the Vital Relays (ACPRs) of each track section picked up?
At the sending end of track section
What is the purpose of providing individual track sections in each direction with resetting facility?
To reset the track section in case of equipment failure
What is the primary purpose of providing track status information at stations?
To ensure safe and efficient train operations
What is the main function of supervisory track sections in automatic signalling?
To provide redundancy in track circuits and axle counters
What is the primary purpose of manual reset procedures in automatic signalling?
To reset individual track sections after failure
What is the primary function of axle counters in automatic signalling?
To detect track vacancy and transmit signals
What is the primary purpose of automatic reset systems in individual track sections?
To minimize downtime and ensure continuous operations
What is the primary purpose of track section management in automatic signalling?
To manage and control individual track sections
What is the primary purpose of level crossing gates in automatic signalling?
To ensure safe and efficient crossing operations
What is the primary purpose of providing LED signal lamps in automatic signalling?
To display signal aspects and gate information
What is the purpose of the L-I automatic reset feature?
To reset a failed track section using a clear track section
What happens when a supervisory track section is clear according to the L-II automatic reset feature?
All track sections falling within the jurisdiction of that supervisory track section are assumed to be clear
What is the condition for a track section to be reset using the L-II automatic reset feature?
The track section is in failure state and the supervisory track section is clear
What is the purpose of the L-III manual reset feature?
To reset all track sections in a section under consideration
What happens to a track section under reset using the L-I automatic reset feature?
It is kept in preparatory mode
What is required for a track section to be reset using the L-II automatic reset feature with a supervisory track section?
A train with low speed must enter and exit the track section with equal count at the boundaries
What is the condition for manual reset to be carried out?
When Level-1 and Level-2 reset fail
What is the purpose of the supervisory track section in the L-II automatic reset feature?
To assume all track sections falling within its jurisdiction are clear
What is the minimum frequency of testing for Track Circuit control on signal and aspect control by signals in advance?
Once in a year
What should be done after every track renewal work to ensure proper working of track circuits/Axle counters?
Adequate precautions should be taken
What should be done to the 'A' marker of the Advanced Starter Signal of the station in rear and Home signal of the station in advance during abnormal conditions?
It should be extinguished
What is the purpose of the Interlocking equipments and circuits for level crossings and points?
To establish the proper working of track circuits
What should be done to failures reported by the Loco Pilots/Motor man?
They should be promptly attended
What is the purpose of the Axle Counter resetting circuits?
To reset the axle counters after a failure
What should be done to the Power Supply system?
It should be adhered to the provisions contained in Chapter 16 of SEM
What should be done to the Cables system?
It should be adhered to the provisions contained in Chapter 15 of SEM
What is the purpose of L-I automatic reset feature?
To reset a track section when a train has cleared both the track sections
What is required for a track section to be reset using the L-II automatic reset feature?
The supervisory track section has to be clear
What happens to a track section under reset using the L-I automatic reset feature?
It is kept in preparatory mode
What is the condition for manual reset to be carried out?
When Level-1 and Level-2 reset have failed
What is the purpose of the L-III manual reset feature?
To reset all track sections in a section under consideration
What happens when a supervisory track section is clear according to the L-II automatic reset feature?
All track sections in the jurisdiction of the supervisory track section are reset
What is the primary purpose of the automatic reset systems in individual track sections?
To reset a track section when it has failed and is under preparatory mode
What is the condition for a track section to be reset using the L-II automatic reset feature with a supervisory track section?
When the supervisory track section is clear
What should be the design principle of fail-safe circuits?
To always assume a safe condition and ensure continuous energization
What is the primary purpose of double cutting arrangements in external circuits?
To prevent any failure from causing an unsafe condition
When a signal is working as an automatic signal, what is the condition for the illuminated 'A' marker to light up?
When the points are set correctly and locked
What should happen to the signal if a lamp of the aspect displayed fails?
The signal should immediately assume the next restrictive aspect
What should happen to a signal which must display a red aspect if it does not do so for any reason?
The signal in rear should display a red aspect
What should be done to ensure the correct setting and locking of the points as required?
Check the setting and locking of the points
What should be done to the circuit for illuminated 'A' marker of a Semi-Automatic Signal?
Ensure the circuit works only when the signal is working as an automatic signal
What is the primary purpose of providing LED signal lamps in automatic signalling?
To enhance the reliability of the signal system
What is the primary requirement for cables in signalling?
To meet the provisions contained in Chapter 15 of SEM
What is the primary requirement for power supply in signalling?
To meet the provisions contained in Chapter 16 of SEM
What is the primary purpose of manual reset with line verification?
To verify the track section status
What is the primary purpose of automatic resetting?
To reset the track section status
How frequently should Track Circuit control on signal and aspect control by signals in advance be tested?
At least once a year
What should be done after every track renewal work?
Take adequate precautions to ensure proper working of track circuits/Axle counters
What should be done to the 'A' marker of the Advanced Starter Signal of the station in rear and Home signal of the station in advance during abnormal conditions?
It should be extinguished
What should be done to failures reported by the Loco Pilots/Motor man?
They should be promptly attended
What is the voltage range required for MSDAC to operate?
19-72 V DC
What is the purpose of the Mini IPS at each AG location?
To provide power supply to EI OCs and MSDAC
What type of cable is used to connect the MSDAC evaluator to each DP?
Quad cable
What is the condition for manual reset to be carried out?
When Station Masters of both stations have ascertained that all track sections are clear of trains
What is the purpose of the reset box at the train sending station?
To manually reset all track sections between both stations
What is the purpose of the Line Verification (LV) box at the other station?
To verify that all track sections are clear of trains
What is the input supply voltage for the Mini IPS?
230 V AC
What is the purpose of the cable from AG to Half location box?
To terminate the signal cable at the signal location
What is the primary purpose of providing a Track Indicator in Automatic Signalling on Single Line?
To indicate if the block section is occupied or clear
What is the purpose of providing media diversity in Axle Counters?
To ensure a reliable and accurate count of axle positions
What is the primary purpose of providing redundancy in Track circuits/Axle Counters in the Automatic Section?
To improve availability in Track circuits/Axle Counters
What is the primary purpose of automatic reset systems in individual track sections?
To reset individual track sections in case of equipment failure
What is the primary purpose of providing individual track sections in each direction with resetting facility?
To reset individual track sections in case of equipment failure
What is the purpose of the 'A' marker on an Automatic Stop Signal?
To identify the signal number
What is the purpose of the enamelled yellow disc with letters 'G' in black on a Semi-Automatic Stop Signal?
To show that the signal is interlocked with a level-crossing
What is the primary purpose of manual reset with line verification?
To verify that the track section is clear before manual reset
Study Notes
Automatic Block Signalling
- Design of Axle Counters between two adjacent stations allows for individual track sections in each direction to have resetting facility from dispatching end station master in case of failure of equipment.
- Redundancy may be provided in Track circuits/Axle Counters in the Automatic Section to improve availability.
- Media diversity shall preferably be provided for Axle Counters.
- Track indicator for Automatic Signalling on Single Line: an indicator shall be provided at each station to indicate whether the block section is occupied or clear.
Markers
- Each Automatic Stop Signal shall be identified by its number and provided with a Marker consisting of a white disc with letter ‘A’ in black.
- A Semi-Automatic Stop Signal shall be provided with a Marker which shall show a white illuminated letter ‘A’ against a black background when the signal works as an Automatic Stop Signal.
- A Signal interlocked with a level-crossing shall be provided with a yellow disc with letters ‘G’ in black and an ‘A’ marker light.
Track Sections and Supervisory Track Sections
- No separate track section has been made for overlap portion of auto-sections.
- A single track section includes route as well as overlap of a signal.
- Supervisory track sections have been formed using the DPs of track sections for automatically resetting the track sections.
- Each supervisory track section covers two (02) track sections.
- Supervisory track sections have overlapping boundaries.
Evaluator (EV) and OFC
- Two evaluators (EVs) (M&R) are provided in each AG 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 MSDACs used in the present scheme have one dedicated COM-AdC board with ethernet port to communicate with adjacent EVs.
Reset Features of MSDAC
- Reset arrangement is proposed at three levels using Track Sections and Supervisory Track Sections, two of which are automatic reset arrangements and one is manual reset.
- L-I: Automatic reset with redundant track section.
- L-II: Automatic reset with Supervisory track section.
- L-III: Manual Reset with Line verification.
Testing and Maintenance
- The following shall be tested by the SSE/JE (Signal) at least once in a year:
- Track Circuit control on signal and aspect control by signals in advance.
- Automatic Cutting-in of the next restrictive aspect when the LED aspect of the main signal fails.
- Interlocking equipments and circuits for level crossings and points.
- The circuits that establish the direction of traffic in Single Line and prevent clearing of conflicting signals on sections provided with Automatic block Signalling on Single Line.
- Axle Counter resetting circuits, if provided.
- All failures reported by the Loco Pilots/Motor man shall be promptly attended.
- Adequate precautions should be taken after every track renewal work to ensure proper working of track circuits/Axle counters.
Power Supply, Cables, and Installation
- Provisions contained in Chapter 16 of SEM shall be adhered to for Power Supply.
- Provisions contained in Chapter 15 of SEM shall be adhered to for Cables.
- Provisions contained in Chapter 17 of SEM shall be adhered to for Track Circuits.
- Provisions contained in Chapter 22 of SEM shall be adhered to for Installation in 25 KV AC electrified areas.
- Extant guidelines on Installation, Testing & Commissioning shall be adhered to.
Modified Semi-Automatic Signalling Working
- Under special instructions, one of the automatic stop signals between two stations in the automatic block signalling territory on Double Line may be made as modified semi-automatic stop signal in each direction.
- The relevant information of Automatic Signalling gears in section should be available/visible at station like Signals Aspects, track status information, Axle Counter reset information, and gate information.
Automatic Block Signalling
- The status of vital relays is read by OCs (Operation Control) and transmitted to the Central Interlocking Unit for logic processing.
- The status of aspects is sent back to corresponding OCs for driving Automatic Signals.
- Reset features of MSDAC (Microprocessor-based Signalling and Digital Axle Counter) include:
- Automatic reset with redundant track section (L-I)
- Automatic reset with Supervisory track section (L-II)
- Manual reset with Line verification (L-III)
Reset Features
- L-I: Automatic reset with redundant track section
- Once the train has cleared both track sections, and any one of the track sections is in failure state, the track section in clear condition will reset the one in fail condition.
- The track section under reset is kept in preparatory mode, and the clear track section information is used to clear the signal.
- 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 its corresponding supervisory track section is clear, it will automatically reset the failed track section.
- 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 track sections in the section under consideration.
Fail-Safe Circuits
- All fail-safe circuits shall work on continuously energized principle.
- Any open circuit in wiring, relay contacts, etc., or loss of power supplies shall not cause an unsafe condition.
Signal Display
- An automatic signal on a double line/single line shall require all tracks to be clear up to the next signal and an adequate distance beyond, before it can display 'OFF' position.
- In case of Single Line, direction of traffic shall also be established.
LED Signals
- LED signals of approved type by RDSO (Research, Designs and Standards Organisation) shall be used.
- All external circuits shall be provided with double cutting arrangements.
Circuit Design
- The circuits shall be so designed that, if the lamp of the aspect displayed fails, the signal shall immediately assume the next restrictive aspect.
- If a signal which must display red aspect does not do so for any reason, the signal in rear shall display a red aspect.
'A' Marker and 'AG' Marker
- The circuit for illuminated 'A' marker of a Semi-Automatic Signal shall be such that the 'A' marker lights up only when the signal is working as an automatic signal.
- The circuit for illuminated 'AG' marker where provided shall be such that the 'AG' marker lights up only when the conditions for 'A' Marker to light up are satisfied except for the level crossing gate which may either be open to road traffic or may have failed.
Power Supply Arrangement
- Each AG is provided with a Mini IPS, for which the input supply of 230 V AC is from UP AT and DN AT at each location.
- The necessary power supplies for EI OCs and 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.
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.
- Automatic Signals at AG are directly fed using a 12 x 1.5 Sq.mm signaling cable from AG, without any repeater relay at site, as the distance is not more than 200 meters.
- Quad Cable: MSDAC evaluator to each DP requires 1 quad of 4 conductor.
- 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.
Testing and Maintenance
- The following shall be tested by the SSE/JE (Signal) at least once in a year:
- Track Circuit control on signal and aspect control by signals in advance.
- Automatic Cutting-in of the next restrictive aspect when the LED aspect of the main signal fails.
- Interlocking equipments and circuits for level crossings and points.
- The circuits that establish the direction of traffic in Single Line and prevent clearing of conflicting signals on sections provided with Automatic block Signalling on Single Line.
- Axle Counter resetting circuits, if provided.
- All failures reported by the Loco Pilots/Motor man shall be promptly attended.
- Track Circuits/Axle Counter Maintenance:
- Adequate precautions should be taken after every track renewal work to ensure proper working of track circuits/Axle counters.
- Provisions contained in Chapter 17 of SEM shall be adhered to.
Modified Semi-Automatic Signalling Working
- Under special instructions, one of the automatic stop signals between two stations in the automatic block signalling territory on Double Line may be made as modified semi-automatic stop signal in each direction.
- During abnormal conditions like fog, bad weather impairing visibility, Modified Semi-Automatic Signal may be worked by extinguishing ‘A’ marker in the manner prescribed under special instructions.
- The design of the Axle Counters between two adjacent stations shall be such that individual track sections in each direction shall have resetting facility from dispatching end station master in case of failure of equipment, with co-operation of receiving end station master for verification of last vehicle.
- Redundancy may be provided in Track circuits/Axle Counters in the Automatic Section to improve availability.
- Media diversity shall preferably be provided for Axle Counters.
- Track indicator for Automatic Signalling on Single Line: An indicator shall be provided at each station to indicate whether the block section is occupied or clear.
This quiz covers the design and operation of track circuits and axle counters in railway signaling systems, including their functionality and failure recovery.
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