Telecom Cable Laying and Termination

Cable Laying

• In busy areas, HDD (Horizontal Directional Drilling) method should be used to lay all types of cables in DWC pipes or approved protection arrangements.
• Where concrete large size duct is provided in the station section for laying signalling cables, the same may be utilized for telecom cables also, following due precautions.

Cable Termination

• Cables can be terminated in DP Box of approved type or through direct termination.
• PIJF cable of various sizes shall be terminated through DP Box of approved type.

Jointing of PIJF Cable

• Jointing should be done by a skilled and experienced person using the correct RDSO specified jointing kit to ensure quality.
• The entire cable laying and jointing to be done under close supervision of telecom staff.
• Thermo shrinkable jointing material shall be used for jointing armoured PIJF cable with thermo shrinkable jointing technique using RDSO's code of practice.
• The jointing material is readily available in the form of a jointing kit, and different kits are used for different sizes of cable (No. of pairs and cond. dia.).

Testing Cable Before Laying

• Before laying, the cable shall be tested for insulation and continuity of the cores.
• Continuity of armour and screen of the cable need to be checked before laying.
• Bedding and armouring of the cable shall also be inspected to see that there has been no damage during transit or in storage.

Laying Out the Cable

• For laying out cables, the cable drums shall be mounted on cable-wheels.
• The drum on the wheel shall be brought to one end of the trench and the end of the cable freed and put into the trench.
• A party of labourers shall follow the drum and guide the cable from the road into the trench carefully so that the cable is not damaged or bent unduly.

General

• While excavating earth for trenches or making other pits necessary for installation of cable junction boxes, the Permanent Way Inspector or his representative shall be present.
• In 'Quad' type of cables, conductors diagonally opposite shall form one circuit.
• In telephone cables, electro-static and electro-magnetic induction between different pairs of conductors shall be minimized by a lead or aluminium sheath and by the provision of twisted pairs.

Line Plant Systems - Underground Copper Cable

• Railway departmental telecommunication lines are usually laid underground between railway offices in railway colonies, large workshops, station yards, and in the block sections alongside the track.
• All telecom lines shall, as far as possible, be laid in a manner that due provisions are kept for any future extensions or extra connection which can be catered for without considerable alteration to the existing circuits or reconstruction of the entire alignment.

Types of Cables Used

• Quad Cable 0.9 or 1.4 mm conductor dia as per IRS specification No.IRS:TC 30/05 is used for control circuits and block interfaces.
• Multi pair (from 10 pairs to 200) Multi Dia (0.5mm/0.63mm/0.9mm) PIJF (Polythene insulated Jelly Filled) Cable as per IRS specification No.IRS:TC 41/97 is used for exchange subscriber lines or branch cables branching off from the main Quad cable.
• Twisted Pair Switch Board Cable of sizes 0.5 mm / 0.6 mm copper conductor dia as per IRS/TEC specification is used for indoor applications such as distribution to various telephone subscribers in a building, MDF to exchange wiring etc.
• RE cable containing paper as well as polythene insulated copper quads should be replaced at the earliest.

Testing Cable Before Laying

• Cable must be tested for insulation and continuity of cores before laying
• Continuity of armour and screen of the cable also needs to be checked before laying
• Bedding and armouring of the cable must be inspected for damage during transit or storage

Laying Out the Cable

• Cable drums must be mounted on cable-wheels for laying out cables
• Drum on the wheel is brought to one end of the trench, and the end of the cable is freed and put into the trench
• Cable-wheels are then drawn along the road or track, and a party of labourers follows the drum to guide the cable into the trench
• In case cable-wheels are not available, the drum is mounted on an axle at one end of the trench, and cable is laid out and carried by labourers

General Guidelines

• Permanent Way Inspector or representative must be present while excavating earth for trenches or making pits for cable junction boxes
• In 'Quad' type of cables, conductors diagonally opposite form one circuit
• Electro-static and electro-magnetic induction between different pairs of conductors in telephone cables must be minimized
• HDD (Horizontal Directional Drilling) method should be used to lay all types of cables in DWC pipes or approved protection arrangement in busy areas
• Concrete large size ducts provided in station sections for laying signalling cables can also be utilized for telecom cables

Cable Termination

• Cables can be terminated in DP Box of approved type or by direct termination
• PIJF cable of various sizes must be terminated through DP Box of approved type

Jointing of PIJF Cable

• Jointing should be done by a skilled and experienced person using the correct RDSO specified jointing kit to ensure quality
• Jointing should be done under close supervision of telecom staff, and video recording may be used to ensure quality of laying and jointing
• Thermo shrinkable jointing material must be used for jointing armoured PIJF cable with thermo shrinkable jointing technique
• Jointing material is readily available in the form of a jointing kit, and different kits are used for different sizes of cables

Line Plant Systems – Underground Copper Cable

• Railway departmental telecommunication lines are usually laid underground between railway offices, large workshops, station yards, and block sections alongside the track
• Telecom lines should be laid in a manner that allows for future extensions or extra connections without considerable alteration to existing circuits or reconstruction of the entire alignment

Types of Cables Used

• Quad Cable with 0.9 or 1.4 mm conductor diameter is used for control circuits and block interfaces
• Multi pair (from 10 pairs to 200) Multi Dia (0.5mm/0.63mm/0.9mm) PIJF Cable is used for exchange subscriber lines or branch cables
• Twisted Pair Switch Board Cable of sizes 0.5 mm / 0.6 mm copper conductor diameter is used for indoor applications
• RE cable containing paper as well as polythene insulated copper quads should be replaced at the earliest