Railway Signaling and Track Circuits

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Questions and Answers

In Hot-standby mode, what happens to track vacancy detection in case of failure of one DP?

Supervisory track section is formed

Track vacancy detection is not affected (correct)

Track section is automatically reset

Track vacancy detection is 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 (correct)

To increase the speed of the trains

To reduce the number of track sections

To reduce the overall cost of the system

What is the purpose of Supervisory track sections?

To overlap track sections

To detect track vacancy

To automatically reset track sections (correct)

To connect to adjacent stations

What is the purpose of the resetting facility in individual track sections?

To reset the track section in case of equipment failure Signup and view all the answers

How many track sections are covered by a single Supervisory track section?

Two Signup and view all the answers

What connects the main DPS of UP and DOWN direction?

EV(M) and EV(R) Signup and view all the answers

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 Signup and view all the answers

What is the purpose of media diversity in Axle Counters?

To improve the reliability of the system Signup and view all the answers

What is the purpose of COM-AdC board in MSDACs?

To communicate with adjacent EVs Signup and view all the answers

What happens if one COM-AdC board fails?

No impact, the system continues to function Signup and view all the answers

What is the purpose of the 'A' marker on an Automatic Stop Signal?

To identify the signal number Signup and view all the answers

What is the purpose of the ethernet switch in Fig. 4?

To transfer evaluated information to OFC Signup and view all the answers

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 Signup and view all the answers

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 Signup and view all the answers

Where are the Vital Relays (ACPRs) of each track section picked up?

At the sending end of track section Signup and view all the answers

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 Signup and view all the answers

What is the primary purpose of providing track status information at stations?

To ensure safe and efficient train operations Signup and view all the answers

What is the main function of supervisory track sections in automatic signalling?

To provide redundancy in track circuits and axle counters Signup and view all the answers

What is the primary purpose of manual reset procedures in automatic signalling?

To reset individual track sections after failure Signup and view all the answers

What is the primary function of axle counters in automatic signalling?

To detect track vacancy and transmit signals Signup and view all the answers

What is the primary purpose of automatic reset systems in individual track sections?

To minimize downtime and ensure continuous operations Signup and view all the answers

What is the primary purpose of track section management in automatic signalling?

To manage and control individual track sections Signup and view all the answers

What is the primary purpose of level crossing gates in automatic signalling?

To ensure safe and efficient crossing operations Signup and view all the answers

What is the primary purpose of providing LED signal lamps in automatic signalling?

To display signal aspects and gate information Signup and view all the answers

What is the purpose of the L-I automatic reset feature?

To reset a failed track section using a clear track section Signup and view all the answers

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 Signup and view all the answers

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 Signup and view all the answers

What is the purpose of the L-III manual reset feature?

To reset all track sections in a section under consideration Signup and view all the answers

What happens to a track section under reset using the L-I automatic reset feature?

It is kept in preparatory mode Signup and view all the answers

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 Signup and view all the answers

What is the condition for manual reset to be carried out?

When Level-1 and Level-2 reset fail Signup and view all the answers

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 Signup and view all the answers

What is the minimum frequency of testing for Track Circuit control on signal and aspect control by signals in advance?

Once in a year Signup and view all the answers

What should be done after every track renewal work to ensure proper working of track circuits/Axle counters?

Adequate precautions should be taken Signup and view all the answers

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 Signup and view all the answers

What is the purpose of the Interlocking equipments and circuits for level crossings and points?

To establish the proper working of track circuits Signup and view all the answers

What should be done to failures reported by the Loco Pilots/Motor man?

They should be promptly attended Signup and view all the answers

What is the purpose of the Axle Counter resetting circuits?

To reset the axle counters after a failure Signup and view all the answers

What should be done to the Power Supply system?

It should be adhered to the provisions contained in Chapter 16 of SEM Signup and view all the answers

What should be done to the Cables system?

It should be adhered to the provisions contained in Chapter 15 of SEM Signup and view all the answers

What is the purpose of L-I automatic reset feature?

To reset a track section when a train has cleared both the track sections Signup and view all the answers

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 Signup and view all the answers

What happens to a track section under reset using the L-I automatic reset feature?

It is kept in preparatory mode Signup and view all the answers

What is the condition for manual reset to be carried out?

When Level-1 and Level-2 reset have failed Signup and view all the answers

What is the purpose of the L-III manual reset feature?

To reset all track sections in a section under consideration Signup and view all the answers

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 Signup and view all the answers

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 Signup and view all the answers

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 Signup and view all the answers

What should be the design principle of fail-safe circuits?

To always assume a safe condition and ensure continuous energization Signup and view all the answers

What is the primary purpose of double cutting arrangements in external circuits?

To prevent any failure from causing an unsafe condition Signup and view all the answers

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 Signup and view all the answers

What should happen to the signal if a lamp of the aspect displayed fails?

The signal should immediately assume the next restrictive aspect Signup and view all the answers

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 Signup and view all the answers

What should be done to ensure the correct setting and locking of the points as required?

Check the setting and locking of the points Signup and view all the answers

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 Signup and view all the answers

What is the primary purpose of providing LED signal lamps in automatic signalling?

To enhance the reliability of the signal system Signup and view all the answers

What is the primary requirement for cables in signalling?

To meet the provisions contained in Chapter 15 of SEM Signup and view all the answers

What is the primary requirement for power supply in signalling?

To meet the provisions contained in Chapter 16 of SEM Signup and view all the answers

What is the primary purpose of manual reset with line verification?

To verify the track section status Signup and view all the answers

What is the primary purpose of automatic resetting?

To reset the track section status Signup and view all the answers

How frequently should Track Circuit control on signal and aspect control by signals in advance be tested?

At least once a year Signup and view all the answers

What should be done after every track renewal work?

Take adequate precautions to ensure proper working of track circuits/Axle counters Signup and view all the answers

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 Signup and view all the answers

What should be done to failures reported by the Loco Pilots/Motor man?

They should be promptly attended Signup and view all the answers

What is the voltage range required for MSDAC to operate?

19-72 V DC Signup and view all the answers

What is the purpose of the Mini IPS at each AG location?

To provide power supply to EI OCs and MSDAC Signup and view all the answers

What type of cable is used to connect the MSDAC evaluator to each DP?

Quad cable Signup and view all the answers

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 Signup and view all the answers

What is the purpose of the reset box at the train sending station?

To manually reset all track sections between both stations Signup and view all the answers

What is the purpose of the Line Verification (LV) box at the other station?

To verify that all track sections are clear of trains Signup and view all the answers

What is the input supply voltage for the Mini IPS?

230 V AC Signup and view all the answers

What is the purpose of the cable from AG to Half location box?

To terminate the signal cable at the signal location Signup and view all the answers

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 Signup and view all the answers

What is the purpose of providing media diversity in Axle Counters?

To ensure a reliable and accurate count of axle positions Signup and view all the answers

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 Signup and view all the answers

What is the primary purpose of automatic reset systems in individual track sections?

To reset individual track sections in case of equipment failure Signup and view all the answers

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 Signup and view all the answers

What is the purpose of the 'A' marker on an Automatic Stop Signal?

To identify the signal number Signup and view all the answers

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 Signup and view all the answers

What is the primary purpose of manual reset with line verification?

To verify that the track section is clear before manual reset Signup and view all the answers

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.

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This quiz covers the design and operation of track circuits and axle counters in railway signaling systems, including their functionality and failure recovery.

Railway Signaling and Track Circuits

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Questions and Answers

In Hot-standby mode, what happens to track vacancy detection in case of failure of one DP?

What is the purpose of providing redundancy in Track circuits/Axle Counters in the Automatic Section?

What is the purpose of Supervisory track sections?

What is the purpose of the resetting facility in individual track sections?

How many track sections are covered by a single Supervisory track section?

What connects the main DPS of UP and DOWN direction?

What is the purpose of providing a Track Indicator in Automatic Signalling on Single Line?

What is the purpose of media diversity in Axle Counters?

What is the purpose of COM-AdC board in MSDACs?

What happens if one COM-AdC board fails?

What is the purpose of the 'A' marker on an Automatic Stop Signal?

What is the purpose of the ethernet switch in Fig. 4?

What is the purpose of the enamelled yellow disc with letters 'G' in black on a Semi-Automatic Stop Signal?

What is the purpose of the 'A' marker light on a Semi-Automatic Stop Signal interlocked with a level-crossing?

Where are the Vital Relays (ACPRs) of each track section picked up?

What is the purpose of providing individual track sections in each direction with resetting facility?

What is the primary purpose of providing track status information at stations?

What is the main function of supervisory track sections in automatic signalling?

What is the primary purpose of manual reset procedures in automatic signalling?

What is the primary function of axle counters in automatic signalling?

What is the primary purpose of automatic reset systems in individual track sections?

What is the primary purpose of track section management in automatic signalling?

What is the primary purpose of level crossing gates in automatic signalling?

What is the primary purpose of providing LED signal lamps in automatic signalling?

What is the purpose of the L-I automatic reset feature?

What happens when a supervisory track section is clear according to the L-II automatic reset feature?

What is the condition for a track section to be reset using the L-II automatic reset feature?

What is the purpose of the L-III manual reset feature?

What happens to a track section under reset using the L-I automatic reset feature?

What is required for a track section to be reset using the L-II automatic reset feature with a supervisory track section?

What is the condition for manual reset to be carried out?

What is the purpose of the supervisory track section in the L-II automatic reset feature?

What is the minimum frequency of testing for Track Circuit control on signal and aspect control by signals in advance?

What should be done after every track renewal work 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?

What is the purpose of the Interlocking equipments and circuits for level crossings and points?

What should be done to failures reported by the Loco Pilots/Motor man?

What is the purpose of the Axle Counter resetting circuits?

What should be done to the Power Supply system?

What should be done to the Cables system?

What is the purpose of L-I automatic reset feature?

What is required for a track section to be reset using the L-II automatic reset feature?

What happens to a track section under reset using the L-I automatic reset feature?

What is the condition for manual reset to be carried out?

What is the purpose of the L-III manual reset feature?

What happens when a supervisory track section is clear according to the L-II automatic reset feature?

What is the primary purpose of the automatic reset systems in individual track sections?

What is the condition for a track section to be reset using the L-II automatic reset feature with a supervisory track section?

What should be the design principle of fail-safe circuits?

What is the primary purpose of double cutting arrangements in external circuits?

When a signal is working as an automatic signal, what is the condition for the illuminated 'A' marker to light up?

What should happen to the signal if a lamp of the aspect displayed fails?

What should happen to a signal which must display a red aspect if it does not do so for any reason?

What should be done to ensure the correct setting and locking of the points as required?

What should be done to the circuit for illuminated 'A' marker of a Semi-Automatic Signal?

What is the primary purpose of providing LED signal lamps in automatic signalling?

What is the primary requirement for cables in signalling?

What is the primary requirement for power supply in signalling?

What is the primary purpose of manual reset with line verification?

What is the primary purpose of automatic resetting?

How frequently should Track Circuit control on signal and aspect control by signals in advance be tested?

What should be done after every track renewal work?

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?

What should be done to failures reported by the Loco Pilots/Motor man?

What is the voltage range required for MSDAC to operate?

What is the purpose of the Mini IPS at each AG location?

What type of cable is used to connect the MSDAC evaluator to each DP?

What is the condition for manual reset to be carried out?

What is the purpose of the reset box at the train sending station?

What is the purpose of the Line Verification (LV) box at the other station?

What is the input supply voltage for the Mini IPS?

What is the purpose of the cable from AG to Half location box?

What is the primary purpose of providing a Track Indicator in Automatic Signalling on Single Line?

What is the purpose of providing media diversity in Axle Counters?

What is the primary purpose of providing redundancy in Track circuits/Axle Counters in the Automatic Section?

What is the primary purpose of automatic reset systems in individual track sections?