Paper II                                          Departmental Practices

 

Time Allowed:        3 hours                         Maximum Marks:         100

 

Instruction to candidates:

  1. Attempt all questions
  2. Marks of each questions are indicated against it
  3. Candidates should read and observe the instructions printed on the cover page of their answer books.
  4. All answers should be written in English only or in Hindi only.
  5. Candidates writing their answers in Hindi Medium must cross check the facts and figures and English-version of the questions. In case of any doubt, difference and discrepancy between the two versions, the English version shall be treated as correct and final.

 

  1. What are various types of subscriber instruments used in the department? How subscriber’s instrument is connected with exchange equipment? Give the diagram showing different points of interconnection from subscriber’s premises to telephone exchange equipment. (3+3+4)

 

a.)        Plan 101 (Parallel Connection within the same room – Bell only in the main instrument)

Plan 102 (Plug & Socket within the building – one portable telephone to be used at different location in the same building. Maximum – 4 sockets)

 

                  Plan 103 (Internal Extension – One main with two internal extensions)

                  Plan 104 (External Extension – One main with one external extension)

Plan 105 (Two telephone with change over switch without intercom facility & signaling facility)

Plan 106 (Two telephone with change over switch with signaling & without intercom facility)

 

b)                  One pair of wire is connected from exchange equipment to sub instrument

Exchange switch->Exchange MDF->UG cable->DP->Drop wire->LJU->instrument                           

                                                     PILLAR                  DP      

                                                   MDF                        

Exchange Switch
 
            c)                                             Primary                               Distribution            Dropwire

 


Instrument
 

 
 
                                                                                                                      LJU 

                                                                                                                                                                                                                                                                                                                                                                                               

                                                                                                                             

 

  1. What is the standard configuration of 128 P CDOT RAX? Name the control cards and ordinary subscribers cards in this RAX? What are the other configurations possible in 128 P CDOT RAX? (5+3+2)

 

            Control Cards:

            RAP                 RAX Administrative Processor

            RSC                 RAX Switch Controller Card.

            SPC /ISP         Signaling Processor Card

            Other cards:

            CNF                Conference Card

            RTC                 RAX Test Terminal Card

            RAT                 RAX Announcement & Tone card

            RMF                RAX Multi frequency card

            RDS                 RAX Digital Signaling

            RDC                RAX Digital Controller

            TC                   Terminal Card ( LCC , CCM , EMF , TWT)

 

            Possible configuration:

 

            By Providing CNF card conference facility & trunk offering facility – 8 ports

            RDS &RDC is used for digital trunks (Slot 22 & 23 should be kept free in case of         RDS & RDC equipped) – 32 ports

            RMF is used for DTMF signaling – 8 ports

            EMF – Ear & Mouth Trunk card (six wires – 2 for signaling & 4 for speech)

                        (to be provided only 3,4,5,&6 slots – each card occupied – 8 ports)

            TWT    Two way trunk for physical trunks – 8 ports

 

  1. What is the capacity of one subscriber rack in  E10B exchange? How many PCMs are required for one subscriber rack? How may subscriber may be connected to one subscriber line card of this exchange? Name the card used for ordinary subscriber and STD PCO subscribers. (3+2+3+2)

 

            The capacity of one subscriber rack in E10B exchange = 1024

 

            PCMs required for one subscriber rack = minimum(2) maximum (4)

 

            Subscribers connected in one subscriber line card = XEJ8 -  8 subscribers

                                                                                                XEJ16 - 16 subscribers

 

            The card used for ordinary subscriber = XEJ16 card

            The card used for STD PCO subscribers = XEJ8 card

 

  1. Give a block diagram of organizational set up of telecom circle. (10)

 

            CGM

            PGM

            GM                              GM(F)

            DGM                           DGM (F) or DFA

            DE /AGM                    CAO

            Senior SDE                  Senior AO

            SDE / AE                     AO

            JTO                             JAO

            TTA                             Senior TOA

            PM                              GR D

            RM

 

  1. What are the different types of earthling used in the department? Describe any one of them with diagram. What is permissible limit of earth resistance for exchange equipment? (4+4+2)

 

            Different types of earthing procedure:

  1. Copper plate earthing
  2. Coil earthing
  3. Ring earthing
  4. Tower earthing

Permissible limit of earth resistance for exchange equipment’s

Tower earth:     Should not be more than 0.1 ohms (the value of tower earth should be less than the equipment earth)

Equipment Earth:          Should not be more than 0.5 ohms

Power Earth     :           Not more than 5.0 ohms (in soft soil)

Not more than 8.0 ohms (in rocky soil)

  1. Write short notes on (4 X 2.5)

a.                   PBX – PBX stands for Private Branch Exchange. It is operated manually. PBX is connected with many extensions. If any lifts the phone, PBX operator got a indication through eye ball indicator, answers the subscriber with answering card by opening the key & connect the other indicator with calling card.

b.                  IDF – Intermediate Distribution Frame is a location where the circuits within the exchanges are interconnected.

c.                   Relays  - Relays are provided to make & break and for switch over in an electrical circuit. There four types of relays used in telecom wing.

i)        600 type – used in subscriber racks

ii)       LS 3000 type – used in selectors

iii)     S&H type – used in trunk boards

iv)     Quinticle type – used cross bar switches

 

d.                  MDF – Main Distribution Frame is an junction point located inside the exchange where the exchange equipment and external lines are inter connected. It has two sides  i) Line Side ii) Exchange Side

 

  1. a. Name any 5 Number of Tools used in line and cable work. Which tool is required for jumpering in Krone type CT boxes? (3+2)

 

1.      Gripping Tool   (to grip the UY connector)

2.      Jack Knife (to open the cable sheath)

3.      Tin cutter (to cut the cable armour)

4.      Measuring Tape (to measure the joint space)

5.      Axa  Frame (To cut the cable)

 

Ø      Insertion Tool (Krone Tool) is required for jumpering in Krone Type CT boxes.

 

b.                  What types of SW board cables are used in department and where they are used?

1.         0.5 mm tinned copper conductor switch board cables

– Exchange to MDF connectivity

2.      0.4 mm tinned copper conductor switch board cables

3.         0.63 mm tinned copper conductor switch board cables

- For stream connectivity

 

  1. a. What is the function of Float rectifier? (5)

 

The function of FR is to receive three phase 440V AC and to give a constant 51.5 volts DC without AC ripples

The steps involved to achieve the functions are

a)                  Step Down – Transformer steps down the 3 phase AC voltage from 440 V to around 80 volts

b)                  Rectification – Any unidirectional device rectifies AC to DC. Diodes & SCR (silicon control rectifier) are used for rectification

c)                  Filtering of AC ripples – Multi stage LC filters are used for filtering the AC ripples.

d)                  Regulation – Regulation is mechanism by which the output of a FR is kept constant at 51.5  + 0.5 v irrespective of input voltage variations of + or – 12%. Output load variations of 5% to 105% and input frequency variations of + or – 4% or 48-52 Hz

 

b. What is the use of engine alternator in telephone exchange?

Ø      In view of the present difficult power supply position, it has become necessary to provide suitable standby power plant equipment

Ø      The exchange system has to  work without any interruption and will not shutdown either partially or totally.

Ø      The above necessitates provision of EA in all the installations.

 

c)What type and capacity of E/A as required for 128 P CDOT  Exchange? (3+2)

 

                        30 KVA engine alternator is required for 128P CDOT exchange.

 

  1. What is lead acid battery ? Mention name of the material used for plates and solution.

 

The electro-chemical device which uses lead and its derivatives and sulphuric acid as its constituent is called lead acid battery.

In a lead acid battery – the positive plate consists of an active material lead oxide and a grid structure of either pure lead or lead alloys which acts as a supporting structure as well as current carrying conductor.

The negative plate consists of spongy lead as active material and pure lead or lead alloy for the grid structure.

The electrolyte used in a lead acid battery is dilute sulphuric acid

 

Give specific gravity and voltage of a charged battery - 1200

       

What is topping up of the cells?

When the acid level of a cell is below the mark, it should be filled up with distilled water up to the top. This process is known as ‘topping up’ of the cell.

 

  1. What is the maximum number of PCMs that can be carried by a 140mb optical fibre system.

 

64 PCMs can be carried by a 140mb optical fibre system

 

List out three  type of tools used for splicing the OF cable and describe its function

 

Three type of tools used for splicing the OF cable

1.      Optical Fibre Stripper

2.      Optical Fibre Cleaver

3.      Optical Fibre Sheath Cutter

4.      Loose tube cutter

 

 

 

 

 

 

 

 

 

 

 

.11.      What is MODEM?

 

            MODEM stands for ‘Modulation & Demodulation’. It converts the analog signals to digital signals & vice versa.

            It can be classified based on speed, Transmission, operation (mode)

Speed  - Low , Medium & high

Transmission – Synchronous  & Asynchronous

Operation – Half Duplex  (two wire) & Full Duplex (Four wire)

 

  1. Different types of computers

 

i)                    Analog Computer

ii)                   Digital Computer

iii)                 Hybrid computer

 

  1. Draw block schematic diagram of a computer & name the parts

 

 

     CPU

MEMORY UNIT

 

 

ALU UNIT

 

 

 

CONTROL UNIT
 
 

 


OUT PUT DEVICE
 

INPUT DEVICE
 
                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                               

Input Device – Keyboard , Mouse, Joy stick

 

CPU – Central Processing Unit

      Memory Unit – ROM &  RAM

      ALU Unit – Arithmetic & logical Unit – It does all the arithmetical & logical functions

      Control Unit – It controls all the peripherals connected to the CPU

 

Output Device – Monitor ( Visual Display Unit), Printer, Plotter