Telecom Cables Overview

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Questions and Answers

What materials are used for the construction of Double Drop wire?

The Double Drop wire is made of copper conductors with diameters of 0.5mm and 0.9mm.

Describe the primary purpose of Field Service (FS) Cable.

FS Cable is used to extend telephone connections for outdoor applications, especially during emergencies.

How does the PVC insulation in Double Drop wire prevent accidents?

The PVC insulation separates L1 and L2, preventing short circuits.

What distinguishes UTP cables from STP cables in data communication?

UTP cables are unshielded while STP cables have shielding for added protection against interference. Signup and view all the answers

Identify one key limitation of UTP cables in LAN setups.

UTP cables are limited to segments no longer than 100 meters. Signup and view all the answers

What are the two types of cables used for LAN networks mentioned in the content?

The two types are Unshielded Twisted Pair (UTP) and Shielded Twisted Pair (STP). Signup and view all the answers

List the standard lengths available for Double Drop wire coils.

The standard lengths are 100 meters, 200 meters, and 500 meters. Signup and view all the answers

What component of FS Cable provides additional mechanical strength?

The steel strands in FS Cable provide additional mechanical strength. Signup and view all the answers

What is the maximum allowed induced voltage in telecommunication circuits during the normal functioning of a power line?

60V Signup and view all the answers

During abnormal conditions in traction power lines, what is the maximum induced voltage that should not be exceeded?

150 Volts Signup and view all the answers

What is the critical current figure recommended by the I.T.U-T to prevent electrostatic induction?

15 mille amperes Signup and view all the answers

What is the psophometric voltage limit for communication circuits to avoid interference with speech transmission?

2mV Signup and view all the answers

What condition induces a maximum of 430V rms in telecommunication circuits?

Traction power line short circuit condition Signup and view all the answers

Why should isolating transformers be introduced every 17 Km along long distance communication networks?

To break metallic continuity and prevent cumulative buildup of induced voltages. Signup and view all the answers

How does electromagnetic interference (EMI) affect data communication over telecommunication cables?

It causes errors, network congestion, and increases packet retransmissions. Signup and view all the answers

What is the implications of strong electromagnetic fields on cables laid along railway tracks?

They induce unwanted current and voltage, leading to psophometric noise and transmission quality degradation. Signup and view all the answers

What are the main advantages of underground (U/G) telecom cables over overhead (O/H) lines?

U/G cables are less susceptible to weather conditions, safer from accidental damage, and have a lower risk of disruptions. Signup and view all the answers

Briefly explain the purpose of the colour code in polythene insulated cables.

The colour code helps identify the function of each conductor within the cable, facilitating easier installation and maintenance. Signup and view all the answers

What is the significance of telecommunication switchboard cables in railway applications?

Telecommunication switchboard cables allow for effective communication between various railway operations and systems. Signup and view all the answers

Describe the impact of 25KV 50 Hz AC traction on telecommunications.

It can cause induction interference in telecom circuits, potentially leading to communication disruptions. Signup and view all the answers

What features distinguish double drop wire from other types of telecom cables?

Double drop wire is characterized by its two parallel conductors, making it suitable for specific telecommunications and transmission applications. Signup and view all the answers

What types of technical data are crucial for understanding telecom cables?

Technical data such as electrical characteristics and physical dimensions are essential for assessing cable performance and compatibility. Signup and view all the answers

What is a key feature of polythene insulated jelly filled cables?

Their jelly-filled construction provides additional moisture protection, enhancing the durability of the cables. Signup and view all the answers

How do underground PIJF cables differ from regular cables?

Underground PIJF cables are specifically designed to be moisture-resistant and suitable for underground installations, reducing the risk of cable damage. Signup and view all the answers

What is the preferred method for tapping circuits according to the text?

The preferred method for tapping circuits is through V.F. Transformers. Signup and view all the answers

What should be done if the trench depth is insufficient?

The lesser depth of the cable trench should be protected with warning bricks. Signup and view all the answers

On what kind of surface should cable drums be stored?

Cable drums should be stored on a well drained, hard surface, preferably paved. Signup and view all the answers

How should cable drums be positioned during storage?

Cable drums should always be stored on their flanges, not on their flat sides. Signup and view all the answers

What moisture prevention method should be taken for cable ends during storage?

Both ends of the cables should be properly sealed to prevent ingress of moisture. Signup and view all the answers

What is the simplest and cheapest method of laying cables according to the content?

The simplest and cheapest method is laying cables direct in the ground. Signup and view all the answers

What is a key feature of the duct system for laying cables?

A key feature is that manholes are provided at definite intervals. Signup and view all the answers

Why is the initial cost of laying ducts considered high?

The initial cost is high due to the complex installation and materials required. Signup and view all the answers

What should be avoided when determining the cable route due to environmental concerns?

Proximity to chemical and paper industries that discharge chemically active effluent should be avoided. Signup and view all the answers

Why is it important to avoid areas prone to water logging when laying cables?

Waterlogged areas can damage cables and complicate maintenance, leading to service interruptions. Signup and view all the answers

What is the recommended separation distance from the nearest track for straight cable runs?

A separation of 10 meters should be kept from the nearest track. Signup and view all the answers

What considerations should be made regarding cable routes near existing tracks?

Cables should not be laid close to existing tracks; instead, they should be positioned near the railway boundary. Signup and view all the answers

How should the orientation of the cable route be determined?

The orientation should be chosen based on distance from other cables and convenience for track crossings. Signup and view all the answers

What is the minimum distance to maintain between OHE masts and cables?

A minimum distance of 5.75 meters should be maintained between OHE masts and cables. Signup and view all the answers

What should be done if special lengths of cable are required for bridges or culverts?

Identify and plan for any special lengths of cable needed to avoid joints on bridges or culverts. Signup and view all the answers

Why is it important to verify pathways and clearances with engineering drawings?

Verifying pathways and clearances ensures compliance with safety standards and prevents future conflicts. Signup and view all the answers

What is the primary benefit of twisting conductors in paired telephone cables?

It reduces electrical interference from neighboring pairs. Signup and view all the answers

How does a ground shield in paired cables function?

It prevents high frequency noise from affecting the signal. Signup and view all the answers

What is a common application for telephone cables in railway systems?

Interconnection of telephones and electronic equipment. Signup and view all the answers

In telecommunications, what is the significance of having no potential difference in twisted pairs?

It prevents current flow and eliminates cross-talk. Signup and view all the answers

What are the diameter options mentioned for paired cables in railway applications?

0.4mm, 0.5mm, and 0.63mm. Signup and view all the answers

How do switchboard cables differ in application from underground PIJF cables?

Switchboard cables are typically used for indoor extensions, while PIJF cables are for outdoor installations. Signup and view all the answers

Explain how the design of twisted pair cables contributes to noise rejection.

The twisting ensures that the net induced voltages on the conductors remain equal. Signup and view all the answers

What specifications are referenced for telecommunication switchboard cables and their significance?

TEC Spec.No: GR/WIR/06/03 ensures compliance with established standards. Signup and view all the answers

What practices should be followed to ensure the protection of staff and equipment in a 25 KV 50 Hz AC traction environment?

Proper grounding, safety equipment usage, and maintaining a safe distance from live wires are essential. Signup and view all the answers

What is the primary difference between PIJF underground paired cables and Quad cables?

PIJF cables have pairs of conductors, while Quad cables consist of four conductors. Quad cables are typically used for higher data transmission capacity. Signup and view all the answers

Which stages are essential in the cable laying process for telecom cables?

Survey work, detailed cable route survey, and cable arrangement in major yards are critical stages. Signup and view all the answers

What are the important types of tests required for 6 Quad PIJF cables before commissioning?

Acceptance tests, mandatory checks, and fault localization tests are crucial. Signup and view all the answers

Describe one method used for jointing underground telecom cables.

The jointing procedure includes preparation of cable ends, aligning conductors, and securing with suitable connectors. Signup and view all the answers

What specific guidelines govern the use of Optical Fiber Cables (OFC) alongside 6 Quad cables in Indian Railways?

Guidelines cover installation methods, protective measures, and integration with existing infrastructure. Signup and view all the answers

Identify one common cause of cable failures and a precaution that may be taken to mitigate it.

Environmental factors, such as moisture penetration, can cause failures. Using moisture-resistant sheathing is a precaution. Signup and view all the answers

What is a significant consideration when laying underground telecom cables near existing tracks?

Maintaining appropriate separation distances to avoid electromagnetic interference is critical. Signup and view all the answers

Explain the significance of a maintenance register for 6 Quad cables.

A maintenance register tracks inspections, repairs, and incidents related to cable performance. Signup and view all the answers

What is the role of cable markers in underground cable laying practices?

Cable markers indicate the locations of buried cables and help prevent accidental damage during construction activities. Signup and view all the answers

What is the maximum longitudinally induced voltage allowed in telecommunication circuits during abnormal functioning?

150 Volts Signup and view all the answers

How does electromagnetic interference (EMI) affect psophometric voltage readings in communication circuits?

EMI can increase psophometric voltage readings, degrading voice and data transmission quality. Signup and view all the answers

What is the role of isolating transformers in long distance communication networks?

Isolating transformers break metallic continuity to prevent cumulative build-up of induced voltages. Signup and view all the answers

What is the recommended screening factor for cables laid along the tracks to mitigate electromagnetic fields?

Less than 0.1 Signup and view all the answers

What psophometric voltage limit must be observed in communication circuits to avoid interference with speech transmission?

2mV Signup and view all the answers

During a short circuit condition in traction power lines, what is the maximum allowed induced voltage in telecommunication circuits?

430V rms Signup and view all the answers

What are the effects of strong electromagnetic fields on the communication cables laid near railway tracks?

Unwanted current and voltage may be induced, causing electrical noise that affects transmission. Signup and view all the answers

What critical figure in milliamperes is recommended by I.T.U-T to limit electrostatic induction in communication circuits?

15 milliamperes Signup and view all the answers

What is the primary difference between CAT5 and CAT5e cables in terms of performance?

CAT5e offers improved crosstalk specifications, allowing for faster data transmission speeds of up to 1Gbps. Signup and view all the answers

Which category of cable can support Token Ring networks and what is its maximum speed?

CAT3 and CAT4 can support Token Ring networks, with CAT3 providing a maximum speed of 10Mbps and CAT4 up to 16Mbps. Signup and view all the answers

What is the role of the physical separator in CAT6 cables?

The physical separator in CAT6 cables reduces electromagnetic interference between the four pairs of wires. Signup and view all the answers

Explain why CAT5e cables are described as 'forgiving' when deployment guidelines are not met.

CAT5e cables are forgiving due to their ability to maintain performance even when installation practices are not ideal. Signup and view all the answers

How does the twisting of pairs in twisted copper wire cables help mitigate interference?

Twisting pairs in the cables helps cancel out interference picked up on one cable by the signal in its partner wire. Signup and view all the answers

What is the maximum transmission speed CAT6 supports, and over what distance?

CAT6 supports speeds of up to 10Gbps for distances up to 55 meters. Signup and view all the answers

What types of network traffic can CAT2, CAT3, CAT4, CAT5/5e, CAT6, and CAT7 support?

These categories can support both computer network traffic and telephone communications. Signup and view all the answers

Which category of Ethernet cable is most commonly used worldwide and why?

CAT5e is the most widely used worldwide due to its cost-effectiveness and ability to support up to 1Gbps. Signup and view all the answers

What depth should pipes be laid below the formation level according to the guidelines?

Pipes shall be laid at a depth of one meter below the formation level or lower as required. Signup and view all the answers

How should the cable be laid when crossing over culverts or in wet areas?

Cables should be laid under the culvert bed through RCC pipes or over the culverts using GI pipes as necessary. Signup and view all the answers

What provisions should be made for laying cables on long bridges regarding temperature changes?

Suitable cable loops should be provided at the pillars to accommodate longitudinal expansion due to temperature differences. Signup and view all the answers

What is the purpose of the two lengths of G.I. wire used in cable installations?

One G.I. wire is for leading in the cable, and the other is kept as an overlay for future cable extraction if needed. Signup and view all the answers

What should be conducted to ensure that damaged cables are not installed during laying on bridges?

The cable drum must be inspected and tested thoroughly prior to installation. Signup and view all the answers

Why is it advisable to have flagmen posted during the cable laying process on bridges?

Flagmen help ensure safety by managing traffic and personnel movement over the bridge during the laying operations. Signup and view all the answers

In what circumstances must the normal dimensions of trenches be adjusted during cable laying?

Normal dimensions should be adjusted when the terrain is rocky. Signup and view all the answers

What considerations should be taken into account for cable laying on roads with special surfaces?

It is beneficial to plan for future expansion by selecting pipe sizes that accommodate later cable drawing. Signup and view all the answers

Study Notes

Telecom Cables (Copper)

Telecom cables are used for telecommunications.
Underground cables are advantageous over overhead lines because they are less susceptible to weather conditions, vandalism, and electromagnetic interference.
The electrical characteristics of telecom cables depend on the type of cable, length, and frequency.

Paired Telephone Cables

Paired cables consist of two insulated wires twisted together to reduce interference.
The types of paired telephone cables include:
- Switchboard cables
- Field service (FS) cables
- Data communication cables
- Coaxial cables
- RF coaxial cables
They are used for various telecommunication applications in railways, including telephone connections, data communication, and radio frequency (RF) transmission.

Underground PIJF Cables

PIJF cables are insulated with polyethylene and filled with a jelly-like material to prevent moisture intrusion
PIJF cables are commonly used for underground telecommunication installations in railways, especially in areas prone to moisture and dampness.
The color code of the conductors in PIJF cables is standardized for identification purposes.

Effects of Railway Electrification on Telecom Circuits

Railway electrification can induce unwanted currents and voltages into telecom circuits due to the electromagnetic fields generated by the traction power system.
This interference can hinder the performance of voice and data communication by causing psophometric noise and data packet errors.
Measures to mitigate the effects of electrification on telecom circuits include:
- Shielding the cables
- Reducing the proximity of the cables to the electrified tracks
- Using isolating transformers
- Selecting suitable cable types with high screening factors.

Cable Laying Practices

Cables should be stored on a well-drained surface to prevent damage and moisture absorption.
Basic methods of laying underground cables include:
- Laying directly in the ground
- Drawing through ducts
Laying directly in the ground is the most common method, and it involves burying the cable in a trench.
Drawing through ducts is used in areas where direct burial is difficult or inconvenient.

Paired Telephone Cables

Paired cables are balanced via two closely spaced conductors twisted together to minimize electrical interference
Twisted pair cabling eliminates cross-talk by ensuring the same net induced voltage across the cables, preventing current flow
Paired cable types: switchboard cables for indoor installation and underground PIJF cables for outdoor extension
Paired cables are used in telecom exchanges, switchboards, telephone wiring, PDH/SDH systems, RS-232 Communication Systems and Digital Transmission networks.
CAT1 wire (untwisted) is typically used for telephone wire. It does not support network traffic and is used for ISDN and PSTN services.
CAT2, CAT3, CAT4, CAT5/5e, CAT6 & CAT 7 wire specifications are suited for network and telephone traffic.
- CAT2 supports speeds up to 4 Mbps.
- Higher network speeds (100 Mbps or higher) require CAT5e or higher.
- CAT5e is the most widely used cabling specification worldwide and is forgiving of deviation from termination and deployment guidelines.
- CAT6 was originally designed to support gigabit Ethernet and is similar to CAT5e, but with a physical separator between pairs to further reduce electromagnetic interference.
- CAT6 supports 1Gbps for up to 100 meters, and 10Gbps for up to 55 meters.

Effects of Railway Electrification on Telecom circuits

Excessively strong electromagnetic fields can induce unwanted current and voltage on cables, which can interfere with voice and data applications.
Excessive electromagnetic interference (EMI) in data communication causes increased errors, network traffic, and congestion.
EMI in analog voice communication creates psophometric noise, which degrades transmission quality.

Cable Laying Practices

DWC pipes should be used for road crossings and laid at a depth of at least one meter below the formation level.
At road crossings, RCC or DWC pipes of specified diameter shall be used.
The size of the pipe should allow for future expansion and accommodate other upcoming cables.
For laying cables under culverts, RCC or DWC pipes should be used.
Cables are laid over culverts using GI pipes according to RDSO/TCDO/COP/13 &14.
Consider temperature differences and provide suitable cable loops at bridge pillars.
Lay cables sinuously inside the GI pipe to accommodate for expansion.
Inspect and test cable drums thoroughly before laying on bridges to prevent damaged cable installation.
Block lines, post flagmen at bridge ends as needed, to ensure staff safety.
In rocky terrain, normal trench dimensions may not be possible.

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Description

This quiz covers various aspects of telecom cables, focusing on copper cables used for telecommunications. It highlights the advantages of underground cables, the characteristics of paired telephone cables, and the features of PIJF cables used in underground installations. Test your knowledge on the different types of cables and their applications!