Telecom Primary MUX Circuits
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Questions and Answers

What is the primary purpose of checking the hour meter readings in a diesel generator set?

  • To test the auto-start feature in case of AC failure
  • To check the battery voltage
  • To determine the fuel efficiency of the generator
  • To schedule maintenance activities accordingly (correct)

    • What is the recommended earth resistance value for the earthing system?

  • Less than 1 ohm (correct)
  • Exactly 1 ohm
  • More than 1 ohm
  • Less than 5 ohms

    • What is the purpose of simulating a fire situation in the fire alarm system maintenance?

  • To check the earthing system's integrity
  • To ensure the air conditioners are working properly
  • To clean the fire sensors
  • To test the fire panels' reporting and analysis capabilities (correct)

    • What is an essential aspect of diesel generator set maintenance?

    <p>Testing on load</p> Signup and view all the answers

    Why is it necessary to check the battery voltage in diesel generator set maintenance?

    <p>To ensure the self-starting capability of the generator</p> Signup and view all the answers

    What is a crucial aspect of air conditioning maintenance?

    <p>Testing the changeover arrangement</p> Signup and view all the answers

    What is the primary objective of earthing system maintenance?

    <p>To prevent electrical shocks and ensure safety</p> Signup and view all the answers

    What is an essential activity in fire alarm system maintenance?

    <p>Cleaning the fire sensors</p> Signup and view all the answers

    What is the frequency of checking the proper functioning of external alarms in an indoor location?

    <p>Yearly</p> Signup and view all the answers

    Who is responsible for verifying the maintenance details during annual inspections?

    <p>Officer in-charge</p> Signup and view all the answers

    What is the frequency of maintenance for air conditioning in an indoor location?

    <p>Yearly</p> Signup and view all the answers

    What is the frequency of checking the earthing system in an indoor location?

    <p>Yearly</p> Signup and view all the answers

    What is the frequency of performing a bit error test on spare time slot/tributary?

    <p>Yearly</p> Signup and view all the answers

    What is the frequency of testing the fire alarm system in an indoor location?

    <p>Yearly</p> Signup and view all the answers

    Where should testing instruments be provided?

    <p>At a centralized location</p> Signup and view all the answers

    What is the frequency of maintenance for diesel generator sets in an indoor location?

    <p>Yearly</p> Signup and view all the answers

    What is the purpose of the alarm system?

    <p>To localize faults to a particular card or sub-system</p> Signup and view all the answers

    Who is responsible for checking the power supply equipment in an indoor location?

    <p>ADSTE/DSTE/Sr.DSTE</p> Signup and view all the answers

    What is the purpose of periodical checks and preventive maintenance?

    <p>To ensure the availability of network</p> Signup and view all the answers

    What type of testing facility should a PCM test set have?

    <p>A to A, A to D, D to A, D to D</p> Signup and view all the answers

    What type of record should be maintained for faults?

    <p>A record of the card, time of failure, duration of failure, and action taken</p> Signup and view all the answers

    How often should the clock frequency be checked?

    <p>Yearly</p> Signup and view all the answers

    What is the minimum duration for which a bit error test on spare time slot/tributary should be performed?

    <p>A week</p> Signup and view all the answers

    What is the primary purpose of the troubleshooting manual?

    <p>To provide a step-by-step procedure for localization of faults</p> Signup and view all the answers

    What is the unit of measurement for 'Total Voltage at Battery' in the Battery Set maintenance checks?

    <p>V</p> Signup and view all the answers

    What is the frequency of checking the 'Engine oil level' in the Diesel Generator Set maintenance checks?

    <p>Frequency not specified</p> Signup and view all the answers

    What is the purpose of the 'Simulation of fire by applying smoke' in the Fire Alarm Check Data List?

    <p>To test the fire alarm system</p> Signup and view all the answers

    What is the unit of measurement for the 'Earth pit' in the Earthing Check Data List?

    <p>Ohms</p> Signup and view all the answers

    What is the purpose of 'Watering of pits' in the Earthing Check Data List?

    <p>To maintain the earth pit's integrity</p> Signup and view all the answers

    What is the purpose of the 'Auto changeover' check in the Air Conditioner Check Data List?

    <p>To ensure the air conditioner's automatic switching</p> Signup and view all the answers

    What is the frequency of checking the 'Cell voltage' in the Battery Set maintenance checks?

    <p>Frequency not specified</p> Signup and view all the answers

    What is the purpose of the 'Checking of protection (X, Y & Z)' in the Battery Charger maintenance checks?

    <p>To check the battery's protection systems</p> Signup and view all the answers

    What is a recommended precaution when handling electronic components?

    <p>Touching a grounded metal surface to discharge static from your body</p> Signup and view all the answers

    What is the recommended frequency for checking the voltage in a multiplexing system?

    <p>3 monthly</p> Signup and view all the answers

    What is the purpose of electro statically sealing the PCB before transporting it to the repair center?

    <p>To prevent electrostatic discharge</p> Signup and view all the answers

    What is the recommended frequency for checking the total distortion in a multiplexing system?

    <p>Yearly</p> Signup and view all the answers

    What is the purpose of using antistatic flooring in a multiplexing system?

    <p>To prevent electrostatic discharge</p> Signup and view all the answers

    What is the recommended frequency for checking the alarm in a multiplexing system?

    <p>3 monthly</p> Signup and view all the answers

    What is the purpose of following a maintenance schedule for multiplexing equipment?

    <p>To prevent equipment failure</p> Signup and view all the answers

    What is the recommended standard for measurements in a multiplexing system?

    <p>All of the above</p> Signup and view all the answers

    What is the primary reason for following a maintenance schedule for multiplexing equipment?

    <p>To reduce equipment downtime and increase overall reliability</p> Signup and view all the answers

    What is the recommended frequency for checking the voltage in a multiplexing system?

    <p>3 monthly</p> Signup and view all the answers

    What is the purpose of using antistatic flooring in a multiplexing system?

    <p>To prevent static electricity from damaging equipment</p> Signup and view all the answers

    What is the recommended frequency for checking the total distortion in a multiplexing system?

    <p>Yearly</p> Signup and view all the answers

    What is the purpose of electro statically sealing the PCB before transporting it to the repair center?

    <p>To prevent damage from static electricity</p> Signup and view all the answers

    What is the recommended standard for measurements in a multiplexing system?

    <p>All of the above</p> Signup and view all the answers

    What is the purpose of alarm checks in a multiplexing system?

    <p>To detect faults in the system</p> Signup and view all the answers

    What is the recommended frequency for checking the idle channel noise in a multiplexing system?

    <p>6 monthly</p> Signup and view all the answers

    What is the minimum system availability required for the Indian Railways Telecom system?

    <p>99.5%</p> Signup and view all the answers

    What is the frame structure of the 2048 Kbps tributary based on?

    <p>ITU-T Rec. G.704</p> Signup and view all the answers

    What is the purpose of time slot 0 in the frame structure of the 2048 Kbps tributary?

    <p>Transmission of frame synchronization word and alarms</p> Signup and view all the answers

    What is the purpose of automatically switching over from one timing signal source to another in case of failure of primary source?

    <p>To ensure synchronization as per approved scheme</p> Signup and view all the answers

    What is the measurement of performance parameters made during the life cycle of the equipment based on?

    <p>Acceptable limits</p> Signup and view all the answers

    What is the purpose of advising S&T control before taking up any maintenance work on telecom equipment?

    <p>To ensure that signalling gears also run on common telecom equipment</p> Signup and view all the answers

    What is the primary requirement for the NMS in terms of management capabilities?

    <p>To check the current status of AC/DC input voltage of each SDH system</p> Signup and view all the answers

    What is the characteristics of complete circuit measured on the basis of?

    <p>Audio frequency 4W/2W interface</p> Signup and view all the answers

    What is the recommended frequency for joint testing of protection channels?

    <p>Once in three months</p> Signup and view all the answers

    What is the multi-frame structure of the 2048 Kbps tributary based on?

    <p>16 consecutive frames numbered from 0 to 15</p> Signup and view all the answers

    What is the primary objective of automatic protection switching?

    <p>To ensure fast restoration of services in case of failure</p> Signup and view all the answers

    What is the primary function of a Terminal MUX?

    <p>To multiplex 30 analogue and/or data channels to a 2048 Kbps digital stream</p> Signup and view all the answers

    What is the minimum number of 2048 Kbps ports required in a PRIMARY DROP/INSERT MUX?

    <p>Two</p> Signup and view all the answers

    What is the requirement for synchronization in SDH equipment?

    <p>Deriving timing signal from internal, external and incoming digital signal tributaries</p> Signup and view all the answers

    What is the upcoming technology for all new work in digital multiplexing equipment?

    <p>IP-MPLS</p> Signup and view all the answers

    What is the primary responsibility of the SSE/JE in terms of maintenance?

    <p>To maintain close liaison with Engineers/Managers of RailTel Corporation of India</p> Signup and view all the answers

    What is the primary requirement for the installation of SDH equipment?

    <p>To follow the guidelines described in para 14.3.8</p> Signup and view all the answers

    What type of cable is used in 25 KV AC electrified areas for media of transmission?

    <p>Star quad cable</p> Signup and view all the answers

    What is the function of DROP/INSERT MUX WITH CONFERENCE FACILITY?

    <p>To provide at least 3 party conferences between any combination of time slots</p> Signup and view all the answers

    What is the primary purpose of revertive systems in protection switching?

    <p>To automatically switch back to the original circuits after restoration of defect</p> Signup and view all the answers

    What is the transmission rate of SDH (STM-1) based hierarchy?

    <p>2048 Kbps</p> Signup and view all the answers

    What is the primary requirement for the system in terms of management capabilities?

    <p>To have management capabilities as per ITU-T G.831</p> Signup and view all the answers

    What is the primary purpose of using Radio based communication as a media of transmission?

    <p>To provide a transmission path in areas where cable installation is not feasible</p> Signup and view all the answers

    What is the primary advantage of using Optical fibre as a media of transmission?

    <p>Higher security</p> Signup and view all the answers

    What is the primary purpose of performing a bit error test on spare time slot/tributary for a period of at least one week?

    <p>To ensure the tributary is functioning correctly</p> Signup and view all the answers

    What is the main advantage of maintaining a systematic record of faults in the multiplexing system?

    <p>It helps in localizing the faults to a particular card or sub-system</p> Signup and view all the answers

    What type of testing facility should a PCM test set have in a multiplexing system?

    <p>A to A, A to D, D to A, D to D testing</p> Signup and view all the answers

    What is the primary function of the alarm system in a multiplexing system?

    <p>To detect and localize faults in the system</p> Signup and view all the answers

    What is the recommended location for providing testing instruments in a multiplexing system?

    <p>At a centralized location</p> Signup and view all the answers

    What is the frequency of performing a bit error test on spare time slot/tributary in a multiplexing system?

    <p>Yearly</p> Signup and view all the answers

    What is the primary purpose of the troubleshooting manual in a multiplexing system?

    <p>To provide a step-by-step procedure for fault localization</p> Signup and view all the answers

    What is the main benefit of maintaining a systematic record of faults in a multiplexing system?

    <p>It facilitates efficient troubleshooting and fault localization</p> Signup and view all the answers

    Study Notes

    Indoor Location Maintenance

    • Every indoor location requires maintenance for electronics, power supply equipment, and other equipment yearly.
    • The officer in-charge should verify the maintenance details during their annual inspections.

    Section Incharge Maintenance

    • The section in-charge is responsible for maintenance of electronics, power supply equipment, and other equipment at various frequencies:
      • Monthly: electronics, power supply equipment
      • Quarterly: DG set, air-conditioning, fire alarm system, general upkeep of equipment room
      • Half yearly: earth
      • Yearly: testing of alarms and its appearance on NMS

    Periodical Checks and Preventive Maintenance

    • Preventive maintenance is necessary for indoor and outdoor equipment to ensure proper upkeep and availability of the network.
    • Diesel Generator Set (DG set) maintenance includes:
      • Testing on load
      • Testing of auto-start in case of AC failure
      • Checking of hour meter readings
      • Checking of diesel oil/engine oil level
      • Checking of oil/air filters
      • Battery voltage (self-start)
      • Cleanliness
      • Water level (in radiator) if applicable
      • Any other check prescribed in the manual
    • Air Conditioning maintenance includes:
      • Working of the air conditioners
      • Working of changeover arrangement, if provided
    • Earthing maintenance includes:
      • Watering of the pits
      • Checking integrity/continuity of the physical connections
      • Tightening of nuts/bolts
      • Checking of earth resistance (value should be less than 1 ohm preferably)
    • Fire Alarm System maintenance includes:
      • Cleaning of fire sensors
      • Simulating the fire situation by applying smoke near to sensors
      • Checking the fire panels for reports and analysis

    General Upkeep of Co-located Equipment

    • Ensure cleanliness
    • Ensure the tower maintenance is done as per schedule by the nominated agency

    Failures

    • The alarm system helps localize faults to a particular card or sub-system.
    • A systematic record of faults must be maintained, indicating the details of the card, time of failure, duration of failure, and action taken to rectify the faults.

    Test Instruments

    • Testing instruments are to be provided at a centralized place or with the maintenance gang.
    • Equipment to be provided at the centralized location includes:
      • PCM test set with facility for A to A and A to D, D to A, D to D testing

    Annexure A: Power Supply Check Data List

    • The list includes items to be checked, frequencies, units, and dates for:
      • Battery Charger
      • Battery Set
      • Diesel Generator Set

    Annexure B: Air Conditioner Check Data List

    • The list includes items to be checked, frequencies, units, and dates for:
      • Cleaning air filter
      • Cooling
      • Load current
      • Cable connections
      • Auto changeover
      • Overhauling

    Annexure C: Fire Alarm Check Data List

    • The list includes items to be checked, frequencies, units, and dates for:
      • Cleaning of sensors
      • Simulation of fire by applying smoke
      • Checking of alarm system

    Annexure D: Earthing Check Data List

    • The list includes items to be checked, frequencies, units, and dates for:
      • Watering of pits wherever necessary
      • Verification of connections
      • Measurement of earth resistance

    Annexure E: Maintenance Format for Fibre Optic System

    • The format includes items to be checked, maintainer, sectional supervisor, and supervisor in charge for:
      • Network Management System
      • Optical Terminal Equipment
      • Maintenance schedule for multiplexing equipment

    System Availability and Performance

    • System availability shall be at least 99.5%.
    • Characteristics of complete circuit shall be measured based on audio frequency 4W/2W interface, following ITU-T G.712 standards.
    • Performance parameters shall be measured during equipment lifecycle, within acceptable limits.

    Synchronization

    • Equipment shall have provision for deriving timing signals from internal, external, and incoming digital signal tributaries.
    • Automatic switching from one timing signal source to another shall occur in case of primary source failure.
    • Synchronization shall be ensured, following approved scheme.

    Frame Structure

    • Frame structure shall conform to ITU-T Rec. G.704/G.732.
    • Frame consists of 32 time slots (0-31), with time slot 0 for transmission of frame synchronization word and alarms.
    • Time slot 16 is for transmission of signalling of channels 1-15 and 16-31.

    Fault Condition and Consequent Action

    • Precautions to be taken while handling electronic components to avoid static discharge.
    • Safety instructions provided by the manufacturer shall be followed.
    • Maintenance schedule for multiplexing equipment shall be followed, with measurements carried out in line with relevant ITU-T standards.

    Maintenance

    • SSE/JE shall maintain close liaison with Engineers/Managers of RailTel Corporation of India (RCIL) for proper maintenance of SDH equipment.
    • Joint testing of protection channels shall be carried out by RailTel and field staff every three months.
    • System shall have provision for manual selection of clock.

    Test Instruments

    • Testing instruments shall be provided at a centralized place or with the maintenance gang.
    • PCM test set with facility for A to A and A to D, D to A, D to D testing shall be provided.

    Digital Multiplexing Equipment

    • Existing digital multiplexing equipment are based on 2048 Kbps SDH (STM-1, STM-4, STM-16 or higher) 10 Mbps, 100 Mbps, 1 Gbps (Ethernet) based hierarchy.
    • New work shall be based on IP-MPLS technology.
    • Media of transmission includes symmetric cable pairs/HDSL modems, star quad cable in 25 KV AC electrified areas, optical fibre, and radio-based communication.

    Primary Multiplexing Equipment

    • Primary multiplexing equipment shall multiplex 30 analogue and/or data channels to 2048 Kbps ITU compatible digital stream on transmit side.
    • On receive side, it shall demultiplex ITU compatible 2048 Kbps digital stream to 30 analogue voice/data channels.
    • Types of primary multiplexers include terminal MUX, primary drop/insert MUX, and drop/insert MUX with conference facility.

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    Description

    Quiz about yearly maintenance of primary MUX circuits, including clock frequency, bit error tests, and alarm systems for fault localization.

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