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Questions and Answers
Railway departmental telecommunication lines are typically installed above ground to connect railway offices.
False
All telecom lines must be designed with considerations for potential future extensions.
True
Quad cable with a 1.4 mm conductor diameter is used exclusively for control circuits.
False
Multi pair cables can have pairs ranging from 10 to 200 and are suitable for underground laying.
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Twisted Pair Switch Board Cable is designed for underground applications.
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RE cable containing paper insulation is recommended for extended use without replacement.
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The IRS specification No. IRS:TC 30/05 outlines the requirements for multi pair cables.
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1.4 mm Quad cable is recommended for block sections that are longer than 12 kms.
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Thermo shrinkable jointing kits are available in various sizes such as TSF-1 and TSF-2.
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Quad cable joints should always be housed underground.
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The screen and armour of copper cables must be connected with suitable wires to ensure proper earthing.
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RTSF type jointing kits are used for armoured PIJF cables.
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Location boxes for cable joints should be painted white with no additional markings.
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The drum must be rolled off onto the road for laying the cable.
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Electro-static and electro-magnetic induction between different pairs of conductors can be minimized by using a lead sheath.
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HDD (Horizontal Directional Drilling) is recommended for laying cables in busy areas.
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Cables can be terminated using any method without adherence to specifications.
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The presence of a Permanent Way Inspector is required while excavating trenches for cable installation.
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The jointing of PIJF cables can be done by anyone without specific skills.
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Concrete large size ducts may be used for telecom cables if necessary precautions are taken.
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Video recording of cable laying is encouraged to ensure quality and depth of trenches.
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0.5 mm conductor diameter twisted pair cables can be used for subscriber connections up to 5 kms.
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Only unarmoured cables are used for underground laying according to standard practices.
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The weight of the 0.63 mm conductor diameter twisted pair cable is 2.81 kg/km.
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Bedding and armouring of the cable do not need to be inspected before laying.
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The size of telephone exchange cables should indicate the number of pairs and type of insulation.
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A party of labours is not necessary when guiding the cable into the trench during laying.
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The 0.6 mm ATC switch board cable is typically used for local subscriber connections within a building.
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The continuity of armour and screen of the cable need not be checked after laying.
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The largest conductor diameter recommended for local subscriber's connections in a building is 0.6 mm.
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The only type of cable suitable for underground laying is armed rubber cable.
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Both insulation and continuity of the cores must be tested before laying the cable.
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2.81 kg/km is the weight of the 0.5 mm conductor diameter twisted pair cable.
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Armoured polythene insulated cables are preferred for high capacity trunk connections.
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Cable drums should be mounted on cable-wheels during the laying process.
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The size of the telephone exchange cables should include both the number of pairs and the weight of the cable.
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The cable laying process does not require supervision to ensure no damage occurs.
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The recommended type of cable for control circuits in block sections longer than 12 kms is the Quad cable with 1.4 mm conductor diameter.
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Twisted Pair Switch Board Cable is primarily designed for underground applications rather than indoor installations.
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Multi pair cables support between 5 to 100 pairs as per the IRS specifications.
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RE cable that contains a combination of paper and polythene insulation is still preferable for use without plans for replacement.
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Cables laid underground must ensure proper earthing by connecting the screen and armour with suitable wires.
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A 0.5 mm conductor diameter twisted pair cable is unsuitable for subscriber connections beyond 3 kms.
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Cable joints for PIJF cables require specific skills for proper execution.
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Multi Dia cables are solely used for control circuits and are not suitable for branch applications.
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Reinforced Thermo Shrink Jelly Filled kits can be used for jointing armoured PIJF cables.
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The copper cables' screen and armour must be earthed with a high value earth connection.
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When using thermo shrinkable jointing material, the jointing kits are standardized regardless of cable size.
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Quad cable joints can be housed in a location box to protect against sharp bends.
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It is essential to first connect the screen and armour of copper cables to prevent electric shocks due to induction.
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A Permanent Way Inspector is not required during the excavation of trenches for cable installation.
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The use of leading or aluminum sheath reduces electro-static and electro-magnetic induction in telephone cables.
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HDD is only recommended for underground cable laying in non-busy areas.
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Cables must be rolled off onto the road for installation purposes to facilitate laying.
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The method of terminating cables can be chosen without following specified standards.
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Jointing of PIJF cables can be performed by any person as long as they have experience.
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Concrete ducts provided in station sections can be utilized for telecom cables with appropriate precautions.
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Video recording of cable laying is discouraged and not permitted.
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Railway departmental telecommunication lines are usually installed underground.
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Multi pair cables are designed solely for control circuits and cannot be used for any other applications.
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Twisted Pair Switch Board Cable is suitable for underground laying.
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1.4 mm Quad cable is recommended for block sections longer than 12 kms.
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RE cable is recommended for use as long as it contains only paper insulation.
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The screen and armour of copper cables must be connected to ensure proper earthing.
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Cable joints for twisted pair cables can be performed by anyone without specific skills.
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The conductor diameter of multi pair cables can vary from 0.5 mm to 0.9 mm.
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The weight of the 0.63 mm conductor diameter twisted pair cable is 2.81 kg/km.
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Outdoor cables can be laid without testing for insulation and continuity.
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Only jelly filled armoured cables should be used when laying cables underground.
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The size of telephone exchange cables should only indicate the type of insulation used.
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The recommended size of the conductor for local subscriber's connection in a building is 0.6 mm.
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Cable layers must ensure no damage occurs during the laying process.
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The continuity of the cable's armour and screen doesn’t need to be checked before laying.
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Concrete ducts may be used for telecom cables if necessary precautions are observed.
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Thermo shrinkable jointing kits are available in different sizes for various cable types.
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Quad cable joints must be placed exclusively above ground.
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The copper cable screen and armour must be earthed with a low value earth.
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The only recommended jointing kit for quad cables is the TSF jointing kit.
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Location boxes for cable joints should be marked with blue stripes.
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Cables should be rolled off onto the road for laying purposes.
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A Permanent Way Inspector must be present while excavating trenches for installing cables.
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Electro-static induction between conductors can be minimized by using a twisted pair configuration.
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Horizontal Directional Drilling (HDD) is necessary only in rural areas for laying cables.
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Video recording of cable laying processes is discouraged.
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Cables can be terminated without following any approved methods.
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Concrete ducts may be used for telecom cables with proper precautions.
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Only skilled persons can perform the jointing of PIJF cables.
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Study Notes
Railway Telecom Line Systems - Underground Copper Cable
- Railway telecommunication lines are usually laid underground between railway offices, workshops, station yards, and along the track.
- Spare capacity should be considered for future extensions or connections to avoid major construction.
Line Plant - Underground Copper Cables
-
Cable types used for various telecommunication circuits:
- Quad cable: 0.9 or 1.4 mm conductor diameter, used for control circuits and block interfaces. 1.4 mm cable is used for longer sections, ideally over 12 km.
- Multi-pair cable: (10 to 200 pairs) with various conductor diameters (0.5mm, 0.63mm, 0.9mm), used for subscriber lines or branch cables.
- Twisted pair switchboard cable: 0.5mm or 0.6mm copper conductor, used for indoor applications like subscriber distribution or exchange wiring.
- RE cable: paper and polythene insulated copper quads should be replaced at the earliest with modern cables.
-
Cables are chosen based on conductor size and application:
-
Outdoor:
- 0.5mm for subscriber connections (up to 5 km).
- 0.63mm for subscriber connections (up to 10km).
-
Indoor:
- 0.5mm ATC for subscriber connections in buildings or exchange wiring.
- 0.6mm ATC for trunk connections.
-
Outdoor:
-
Exchange cable specification:
- Includes number of pairs, conductor diameter, insulation, sheathing, and whether it’s filled, armoured, or unarmoured.
- Only jelly-filled armoured cables should be used for underground laying.
-
Testing Before Laying:
- Test for insulation and continuity of cores, armour, and screen.
- Inspect bedding and armouring for any damage.
-
Cable Laying:
- Drums are mounted on cable wheels and drawn along the route, guiding the cable into the trench carefully.
- In the absence of wheels, drums can be mounted on axles or carried by laborers.
- Never roll the drum off or drag cable on the ground.
-
General Considerations:
- Permanent Way Inspector or representative should be present during excavation near tracks for junction boxes.
- In quad cables, conductors diagonally opposite each other form a circuit.
- Lead or aluminum sheathing and twisted pairs minimize electromagnetic induction between conductors.
- Use HDD (Horizontal Directional Drilling) for crossing roads or rail lines in busy areas, guiding cables through DWC pipes or other approved protection.
- Large concrete cable ducts in station sections can be used for telecom cables with appropriate precautions.
-
Cable Termination:
- Terminated using DP boxes of approved type or directly.
- PIJF cables of various sizes are terminated through DP boxes.
-
PIJF Cable Jointing:
- Done by skilled personnel using RDSO-specified jointing kits.
- Work should be supervised by telecom staff.
- Video recording can be used to ensure quality of cable laying and jointing.
- Thermo shrinkable jointing material is used with thermo shrinkable jointing techniques using RDSO's code of practice.
- Different jointing kits (TSF-1, TSF-2) are available for different cable sizes. Use reinforced thermo shrink jelly-filled kit (RTSF) for quad cables.
- Quad cable joints can be kept underground or inside a location box of appropriate size, avoiding sharp bends.
- Location boxes with joints should have EC Sockets and be marked with black and yellow stripes.
- Screen and armour of copper cables need to be jointed with suitable wires for proper screening and earthing at stations. This is essential to prevent electric shock.
-
Earthing:
- Copper cable screen and armour should be earthed with a low value earth.
Underground Cable Systems
-
Railway telecommunication lines are often laid underground between railway offices, workshops, stations, and block sections.
-
Spare capacity must be built into the system design for future expansion.
Types of Underground Cables
-
Quad Cable: Used for control circuits and block interfaces.
- 0.9 mm or 1.4 mm conductor diameter.
- 6 quad polythene insulated, jelly-filled cable (PIJF).
- 1.4 mm diameter cable suitable for longer block sections (over 12 km).
-
Multi-Pair Cable: Suitable for subscriber lines or branches off the main quad cable.
- 10 to 200 pairs, 0.5 mm/0.63 mm/0.9 mm conductor diameter.
- Polythene insulated, jelly-filled cable (PIJF).
-
Twisted Pair Switchboard Cable:
- 0.5 mm or 0.6 mm copper conductor diameter.
- Used for indoor applications like building distribution and MDF-to-exchange wiring.
-
RE Cable (Paper and Polythene Insulation):
- Planned to be replaced with PIJF cables.
Cable Sizes
-
Outdoor Underground:
- 0.5 mm (1.83 kg/km): Subscriber connections up to 5 km.
- 0.63 mm (2.81 kg/km): Subscriber connections up to 10 km.
-
Indoor:
- 0.5 mm ATC (1.76 kg/km): Local subscriber connections, exchange to MDF wiring.
- 0.6 mm ATC (2.52 kg/km): Trunk connections.
-
Exchange Cables:
- Specification indicates number of pairs, conductor diameter, insulation type, sheath, jelly filled, armoured (or unarmoured).
- Only jelly-filled armoured cables are used for underground installations.
Cable Testing and Laying
-
Pre-Laying Testing:
- Insulation and core continuity tested.
- Armour and screen continuity checked.
- Bedding and armouring inspected for damage.
-
Laying:
- Cables are laid from drums mounted on cable wheels.
- The drum is brought to one end of the trench, and the cable is carefully guided into the trench.
- The cable wheels are drawn along the road or track.
- Labourers follow the drum and guide the cable, ensuring no damage or excessive bending occurs.
General Guidelines
- Excavation: Permanent Way Inspector or their representative must be present during excavations near track areas.
-
Induction Minimization:
- Lead or aluminium sheaths and twisted pairs are used to minimize electrostatic and electromagnetic induction between conductors.
-
Road and Rail Crossings:
- HDD (Horizontal Directional Drilling) method used in busy areas for all cable types.
- Cables installed in DWC pipes or approved protective arrangements.
-
Station Section Ducts:
- Concrete ducts in station sections may be used for telecommunication cables after proper precautions.
-
Quad Cable Circuits:
- Conductors diagonally opposite each other form a single circuit.
Cable Termination and Jointing
- Cable Termination Options:
- DP Box (approved type)
- Direct Termination
-
PIJF Cable Termination:
- Terminated through approved DP boxes.
-
PIJF Cable Jointing:
- Performed by skilled personnel using RDSO-specified jointing kits.
- Close supervision by telecom staff is required during jointing.
- Video recording may be used to document the process and ensure quality.
- Thermo-shrinkable jointing material used for armoured PIJF cable with RDSO code of practice.
- Jointing kits (TSF-1, TSF-2, etc) available for various cable sizes.
-
Quad Cable Joint:
- May be placed underground or in a location box.
- Location box must have an EC socket and be painted with black and yellow stripes.
-
Screen and Armour Connection:
- Jointed using suitable wires.
- Earthing is essential to achieve the specified screening factor and prevent electric shock.
Underground Copper Cable Systems
- Railway telecommunication lines are laid underground between railway offices, workshops, station yards, and along tracks.
- Spare capacity is essential for future extensions and connections.
Line Plant Types and Parameters
- Quad Cable: 0.9 or 1.4 mm conductor diameter, polythene insulated, jelly-filled. Suitable for underground laying, used for control circuits and block interfaces. 1.4 mm conductor diameter is preferred for block sections longer than 12 km.
- Multi Pair Cable: 10 to 200 pairs, 0.5 mm/0.63 mm/0.9 mm conductor diameter, PIJF (Polythene Insulated Jelly Filled). Suitable for underground laying, used for exchange subscriber lines or branch cables.
- Twisted Pair Switch Board Cable: 0.5 mm / 0.6 mm copper conductor diameter. Not designed for underground laying, used for indoor applications like distribution to subscribers, MDF to exchange wiring.
- RE Cable: Paper and polythene insulated copper quads. Should be replaced with newer cable types as soon as possible.
Cable Sizes and Configurations
-
Outdoor Underground:
- 0.5 mm conductor diameter PIJF: Subscriber connections up to 5 km
- 0.63 mm conductor diameter PIJF: Subscriber connections up to 10 km
-
Indoor:
- 0.5 mm ATC Switch Board cable: Local subscriber connections, exchange to MDF wiring
- 0.6 mm ATC Switch Board cable: Trunk connections
-
Exchange Cable Specifications:
- Number of pairs
- Conductor diameter
- Insulation/sheath type
- Jelly filled, armoured or unarmoured
Cable Testing and Laying
-
Pre-Laying Testing:
- Insulation and continuity of cores
- Continuity of armour and screen
- Inspection of bedding and armouring for damage
-
Laying Procedure:
- Cable drums mounted on cable wheels
- Drum brought to one end of the trench, cable end freed and put into the trench
- Cable wheels drawn along the road or track
- Laborers guide the cable into the trench carefully
- If wheels are unavailable, the drum is mounted on an axle and laborers carry the cable
- Never roll the drum directly on the road or drag the cable on the ground
- Permanent Way Inspector or representative must be present when excavating near tracks
Cable Termination and Jointing
-
Termination Methods:
- Approved DP Box
- Direct termination
-
PIJF Cable Termination:
- Through approved DP Box
-
PIJF Cable Jointing:
- Skilled and experienced personnel using RDSO specified jointing kits
- Close supervision by telecom staff
- Video recording recommended for quality assurance
- Thermo shrinkable jointing material for armoured PIJF cable
- Different jointing kits for different cable sizes (TSF-1, TSF-2, etc.)
- Reinforced Thermo Shrink Jelly Filled (RTSF) kit for quad cable
- Quad cable joints can be kept underground or inside a location box
- Location boxes with joints should have EC sockets and be painted black and yellow
-
Screen and Armour Jointing:
- Connect with suitable wires to ensure screening factor and earth connection at stations
- Done first to prevent electric shock due to induction
- Copper cable screen and armour should be earthed with a low value earth
Cable Laying in Busy Areas
- Use HDD (Horizontal Directional Drilling) method to lay cables in DWC pipes or approved protection arrangements when crossing roads or railroads in busy areas.
- Utilize concrete ducts in station sections for laying signaling cables, following precautions.
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Description
Explore the fundamentals of railway telecommunication systems, focusing on underground copper cable types and their applications. This quiz covers various cable specifications, including quad, multi-pair, and twisted pair switchboard cables. Understand the importance of spare capacity for future extensions in railway communication.
