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Questions and Answers
What is the primary function of the underground telecommunication lines mentioned in the content?
To connect railway offices, workshops, station yards, and block sections along the railway tracks.
Why is it necessary to keep spare capacity in telecom lines laid underground?
To allow for future extensions or extra connections without major alterations to the existing circuits.
What distinguishes the 1.4 mm Quad cable from the 0.9 mm Quad cable?
The 1.4 mm Quad cable is used for longer block sections, specifically over 12 km.
What type of cable is generally used for exchange subscriber lines?
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Identify one type of cable that is unsuitable for underground laying.
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What should be done with RE cables containing paper insulation?
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According to IRS specifications, what cable type is suitable for control circuits and block interfaces?
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How many pairs can a Multi pair cable accommodate as mentioned?
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What type of jointing material is recommended for armoured PIJF cable according to the RDSO specifications?
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How are the jointing kits differentiated for various sizes of cable?
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Which jointing kit should be used for quad cables as per the latest specifications?
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What should be done to the joint if it is kept inside a location box?
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Why is it essential to connect the screen and armour of copper cables before jointing?
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What specifications must be included when defining the size of telephone exchange cables?
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Which type of cable is recommended for underground laying according to the guidelines?
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What initial tests should be conducted on the cable before laying it?
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What is the use of a 0.5 mm conductor diameter twisted pair cable?
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What equipment is used for laying out cables according to the guidelines?
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What precautions must be taken when laying the cable if wheels are not available?
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Why is it important to check the bedding and armouring of the cable before laying?
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Which inspector must be present when excavating trenches for cable installation?
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What type of cable is the 0.6 mm ATC Switch Board cable used for?
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How does the design of 'Quad' type cables manage circuit formation?
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How does the specifications format facilitate cable identification for use?
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What method should be employed for cable laying at busy road or rail crossings?
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What type of junction box is approved for terminating PIJF cables?
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What is required for proper jointing of PIJF cables?
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What role does video recording play in the cable laying and jointing process?
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What should be done before utilizing concrete ducts in station sections for telecom cables?
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What is the maximum conductor diameter used for Quad cables suitable for longer block sections?
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Describe the insulation types used for the RE cable mentioned in the content.
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What specification number is associated with multi pair cables as per the content?
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What performance parameter is crucial for planning future extensions in telecom lines?
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What is the conductor diameter range for twisted pair switch board cables as per IRS/TEC specifications?
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Which type of cable is specified for control circuits and block interfaces?
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What characteristic distinguishes multi pair cables from Quad cables in telecom applications?
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Why are twisted pair switch board cables not suitable for underground applications?
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Explain the significance of using different jointing kits like TSF-1 and TSF-2 for varying cable sizes.
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Describe the precautions that must be taken when installing a joint inside a location box for a quad cable.
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What is the importance of earthing the copper cable screen and armour during jointing?
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Why should the jointing of thermo shrinkable joints only be performed following RDSO's code of practice?
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What is the required action for the location box if a joint is placed inside it?
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What method should be used when encountering busy areas for laying cables which involve road or rail crossings?
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Which components are necessary to minimize electro-static and electro-magnetic induction in telephone cables?
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What is the requirement regarding supervision during the jointing of PIJF cables?
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In the absence of wheels, how should the drum be set up for cable laying?
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What should happen to the joint if it is kept inside a location box?
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Why is the use of a skills and experienced person essential during cable jointing?
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What type of termination method is specified for various sizes of PIJF cables?
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What precaution should be taken when utilizing large concrete ducts for telecom cables?
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What specifications are included when defining the size of telephone exchange cables?
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What are the key tests that should be performed on cables before they are laid?
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What is the significance of using only jelly filled armoured cables for underground laying?
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How should cable drums be handled during the laying process?
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What materials are suggested for jointing PIJF cables according to specifications?
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What should be inspected regarding bedding and armouring of the cable before laying?
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In what context is a 0.5 mm conductor diameter twisted pair cable used?
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What precautions are necessary when laying out cables to prevent damage?
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What jointing kits are used for different sizes of cables according to RDSO specifications?
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What specific jointing kit should be used for quad cables?
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What is essential to do with the copper cable screen and armour during jointing?
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What should be done if the joint is kept inside a location box?
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Why is earthing of copper cable screen and armour important?
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What is the conductor diameter of the quad cable suitable for longer block sections?
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Which specification number is associated with multi pair cables?
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What type of insulated cable is recommended for control circuits?
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Why is it necessary to provide provisions for future extensions in telecom lines?
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What insulation types are used in the RE cable mentioned?
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What size of twisted pair switch board cable is indicated for indoor applications?
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What is the maximum number of pairs a multi pair cable can accommodate?
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Which type of cable is specifically unsuitable for underground laying?
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What size of conductor is specified for subscriber connections up to 10 km?
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What type of cables should be used for underground laying?
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What tests must be conducted on the cable before it is laid?
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How should the cable be laid out according to the guidelines?
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What is the purpose of inspecting the bedding and armouring of the cable?
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What size conductor is used for local subscriber's connection in a building?
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What specifications should be included when defining telephone exchange cables?
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What happens to the cable-end when laying it in a trench?
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How should the drum be set up in the absence of wheels when laying cable?
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What methods can be used for terminating cables?
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What precautions should be taken when using concrete ducts for telecom cables?
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What is the requirement for laying cables in busy areas with road or rail crossings?
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Who must be present while excavating for cable installation?
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What should be done prior to jointing PIJF cables?
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What is the significance of utilizing twisted pairs in telephone cables?
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How can quality ensurement be maintained during cable laying and jointing?
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Study Notes
Underground Copper Cable - Line Plant Systems
- Railway departmental telecommunication lines are normally laid underground between railway offices, workshops, and track sections.
Spare Capacity
- All lines should be laid with future expansion in mind, minimizing necessary circuit alterations or complete realignment.
Underground Copper Cable Types and Performance Parameters
- Quad Cable (0.9 or 1.4 mm conductor diameter) - used for block interfaces and control circuits; 1.4 mm is preferred for distances over 12 kilometers.
- Multi Pair Cable (10 to 200 pairs, 0.5, 0.63, or 0.9 mm conductor diameter) - used for exchange subscriber lines and branching off from main quads.
- Twisted Pair Switchboard Cable (0.5 or 0.6 mm copper conductor diameter) - used for indoor applications like telephone subscriber distribution, MDF to exchange wiring, etc.
- RE Cable (paper and polythene insulated copper quads) - ideally replaced with newer types.
Cable Sizes
-
Outdoor Underground:
- 0.5 mm conductor diameter - subscriber connections up to 5 km.
- 0.63 mm conductor diameter - subscriber connections up to 10 km.
-
Indoor:
- 0.5 mm Annealed Tinned Copper - local subscriber connections in buildings, exchange to MDF wiring.
- 0.6 mm Annealed Tinned Copper - trunk connections.
-
Exchange Cables:
- Specify the number of pairs, conductor diameter, insulation/sheath type, jelly filled, armoured or unarmoured.
- Only jelly filled armoured cables are used for underground laying.
Testing Cable Before Laying
- Conduct insulation and continuity tests of cores, armor, and screen.
- Inspect bedding and armoring for damage during transit or storage.
Laying Out the Cable
- Use cable wheels to mount drums. Start at one end of the trench and carefully guide the cable into the trench.
- If wheels aren't available, mount the drum on an axle and carry the cable manually.
- Avoid rolling the drum on the road or dragging the cable on the ground.
General Notes
- Permanent Way Inspector should be present when excavating near tracks.
- In quad cables, diagonally opposite conductors make up a circuit.
- Lead or aluminum sheathing and twisted pairs minimize electromagnetic and electrostatic induction in telephone cables.
- Use Horizontal Directional Drilling (HDD) to lay cables through road or rail crossings in busy areas. Utilize existing concrete ducts in station areas with caution.
Cable Termination
- Terminate cables using:
- DP Box of approved type.
- Direct termination.
- PIJF cables of various sizes should be terminated through DP Boxes.
PIJF Cable Jointing
- Jointing should be done by a skilled person using RDSO specified jointing kits.
- Close supervision of telecom staff required. Video recording can be used to ensure quality.
- Use thermo shrinkable jointing material for armored PIJF cables with thermo shrinkable techniques.
- Use reinforced thermo shrink jelly filled kit (RTSF) for quad cable.
- Quad cable joints can be kept underground or housed in a location box.
- When a joint is housed in a location box, an EC Socket should be fixed on the box and painted black and yellow stripes.
- Screen and armor of copper cables should be jointed with suitable wires to achieve the specified screening factor. Earth this first to avoid electric shock.
- Copper cable screen and armor should be earthed at stations with a low-resistance earth.
Underground Copper Cable for Railway Telecommunications
- Railway telecommunication lines are laid underground, connecting offices, workshops, and stations.
- Spare capacity is important for future extensions and connections without requiring extensive modifications.
-
Various types of underground cables are used:
- Quad Cable: For control circuits and block interfaces.
- Multi-pair Cable: Used for subscriber lines and branch cables.
- Twisted Pair Switch Board Cable: For indoor applications such as building distribution and exchange wiring.
- RE Cable: Should be replaced with newer types as soon as possible.
-
Cable sizes depend on the circuit:
- Outdoor: 0.5 mm and 0.63 mm conductor diameter cables are used for subscriber connections.
- Indoor: 0.5 mm and 0.6 mm ATC Switch Board cables are used for local subscriber connections and trunk connections.
- Telephone exchange cables are specified by the number of pairs, conductor diameter, insulation/sheath type, and whether they are jelly-filled, armored, or unarmoured.
-
Testing and inspection are crucial before cable laying:
- Insulation and core continuity are tested.
- Armour and screen continuity are checked.
- Bedding and armoring are inspected for damage.
-
Cable laying procedures:
- Cables are rolled out from drums mounted on cable wheels.
- Laborers guide the cable into the trench.
- Drums should not be rolled on the road and cables should not be dragged on the ground.
-
General considerations regarding the cable installation:
- Permanent Way Inspector must be present during excavation near tracks.
- 'Quad' type cables have conductors forming a circuit diagonally opposite each other.
- Electrostatic and electromagnetic induction is minimized using a lead or aluminum sheath and twisted pairs.
- Horizontal Directional Drilling should be used in busy areas for road and rail crossings.
- Existing large ducts in station sections can be used for telecom cables with precautions.
-
Cable termination options:
- DP Box of approved type.
- Direct termination.
- PIJF cables are terminated through DP Boxes.
-
Jointing of PIJF Cable:
- Done by experienced personnel with RDSO specified jointing kits.
- Video recording of laying and jointing for quality assurance.
- Thermo shrinkable jointing technique is used for armored PIJF cables.
- Quad cables use Reinforced Thermo Shrink Jelly Filled (RTSF) jointing kits.
- Quad cable joints can be underground or housed inside location boxes avoiding sharp bends.
- The screen and armour of copper cables are jointed using suitable wires for screening and earthing.
- Copper cable screen and armour are earthed with low value earth.
Underground Copper Cable Systems
- Railway telecommunication lines are laid underground between railway offices, workshops, station yards, and trackside block sections.
- All telecom lines should be laid with future expansion in mind, allowing for extra connections without major modifications.
Types of Underground Cables
- Quad Cable: 0.9 or 1.4 mm conductor diameter, polythene insulated, jelly-filled (PIJF), suitable for control circuits and block interfaces. 1.4 mm conductor diameter is preferred for longer block sections (over 12 km).
- Multi-pair PIJF Cable: 10-200 pairs, various conductor diameters (0.5 mm, 0.63 mm, 0.9 mm), used for exchange subscriber lines or branch cables.
- Twisted Pair Switch Board Cable: 0.5 mm or 0.6 mm copper conductor diameter, not designed for underground laying, used indoors for subscriber distribution in buildings, MDF to exchange wiring, etc.
- RE Cable: Older cable type with paper and polythene insulation, planned to be replaced with newer PIJF cables.
Cable Sizes
-
Outdoor Underground:
- 0.5 mm conductor diameter twisted pair PIJF: Subscriber connections up to 5 km.
- 0.63 mm conductor diameter twisted pair PIJF: Subscriber connections up to 10 km.
-
Indoor:
- 0.5 mm Annealed Tinned Copper (ATC) Switch Board cable: Local subscriber connections in buildings, exchange to MDF wiring.
- 0.6 mm ATC Switch Board cable: Trunk connections.
-
Telephone exchange cables: Should be specified with the number of pairs, conductor diameter, insulation/sheath type (e.g., polythene), jelly-filled, armoured, or unarmoured.
- Underground laying requires only jelly-filled, armoured cables.
Cable Testing and Laying
- Before laying, cables must be tested for insulation and continuity of the cores. Continuity of armour and screen should also be checked.
- Bedding and armouring should be inspected for transit or storage damage.
- Cables should be laid out using cable wheels or an axle for support, guiding the cable into the trench carefully to avoid damage.
- Never roll the cable drum directly on the road or drag the cable along the ground.
General Cable Laying Practices
- Permanent Way Inspector or a representative should be present during trench excavation for cable junction boxes near tracks.
- In 'Quad' cables, conductors diagonally opposite form a circuit.
- Telephone cables use lead or aluminium sheaths and twisted pairs to minimize induction.
- Use Horizontal Directional Drilling (HDD) to lay cables across roads and tracks in busy areas, using DWC pipes or approved protection arrangements.
- Utilize concrete ducts in station sections for telecom cables, following safety precautions.
Cable Termination and Jointing
- Termination methods:
- DP Box (approved type)
- Direct Termination
- PIJF cables are terminated using approved DP boxes.
- Jointing of PIJF cables:
- Only skilled and experienced personnel, using RDSO specified jointing kits, should perform jointing.
- Work should be closely supervised by telecom staff, and video recording can be used for quality control.
- Thermo shrinkable jointing material is used for armoured PIJF cables, using the RDSO's code of practice.
- Joint kits are available for different cable sizes (number of pairs, conductor diameter).
- Quad cable joints can be underground or housed inside location boxes (avoiding sharp bends), with EC sockets attached to the location box and painted with black and yellow stripes.
- Screen and armour of copper cables should be jointed using suitable wires to maintain screening factor and earthing at stations, preventing electric shock from induction.
- Copper cable screen and armour should be earthed with low-value earth.
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Description
This quiz covers essential aspects of underground copper cable systems used in railway telecommunication. Topics include types of cables, their performance parameters, and considerations for future expansion. Test your knowledge on quad cables, multi-pair cables, and more.