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We as engineering students are studying theory subjects and some particles. So, that we may not feel short of practical training which will be useful in our job, The University of Rajasthan has provided us with a 45 days training slot to help us learn better. Theory along with practical is always good as it makes us learn quickly. Also in this world of tough and growing competition it will help in keeping our nose ahead of others. It also gives us confidence to work in a company and bring laurels to our country by our good and admirable job.



Short Term

             The short term effect of the implant training was that I realized the importance of time. We have to reach on time in the company. We are also expected be in a proper dress code so that we don’t look out of place and oddly different. I have learned to be sharp, precise and accurate in my work and to finish it on time to gain maximum profit. I have learned to communicate with my colleagues and seniors.


Long Term

             The industrial training will help me in securing a job. Now, I also have some experience of working in a company and abiding by its rules. It also help me in facing questions from a group of persons.


1.     Introduction

2.     Assembly

3.     Tank Intercom System

4.     Back Up Battery

5.     Quality & Assurance

6.     Reliability & Environmental Lab

7.     Project

8.     Conclusion


        Set up in 1954 for defence electronics, BEL manufactures radars, sonars, communication network, electronic warfare systems, electro optics, tank electronics, broadcasting equipment, components, electronic voting machine, photovoltaic systems and other high tech products. It has nine manufacturing units at different locations of India. BEL spends 4 to 5% of its annual revenue on R & D. 60% of its revenue is from indigenously developed products. It employs 12,390 people including 1200 R & D engineers. BEL has been ranked first among medium-sized aerospace/defence companies worldwide in 2003 & 2004.

        It has come a long way since its inception in 1954 and today is hailed as one of the top professional electronics companies, not just in India but around the world.

Profit 2004-05 Rs 4460 million, Revenue Rs 32,120 million.

       The special processes in use in the company are Nut Riveting, Helix Coils & special kind of PCB’s.

Why are helix coils used?

· The tank is a very huge and bulky unit.

· It has to be made of a metal to give it strength and to withstand stress and strain during exercises and war.

· If it is made up of plastic to make it light, it will disintegrate easily.

· Hence, to make it light we should use a light metal.

· Aluminium is a metal which is both light and has good mechanical strength.

· But, Aluminium is also a very soft metal.

· In a tank assembly various fastners would be required.

· To repair and for testing purpose they would be required to be again & again fastened or loosened. This   can damage the soft Aluminium and hence cause the holes to expand.

· So, after drilling the holes, helix coils are used in the holes and the screws tightened.

· The helix coils are made up of steel and are not soft and solve our purpose.

Nut Riveting 

  • Nut riveting is a special type of riveting only used for defense purpose.
  • The tank is fast becoming more & more dependent on electronics.
  • PCB is a very important part of this.
  • A tank has to move through various terrains. It could be rough or smooth, uneven or mountainous.
  • The connections on the PCB should not break during operation which could lead to the failure of the whole system.
  • To avoid this nut riveting is used.
  • It is a special type of rivet which is tapered from the bottom to lock into the PCB and hence make the connection permanent.
  • This riveting can also be used when we have very thin thread or no possible access to nuts through the other side.


Special PCB’s

  • For commercial purpose PCB made up of Paper Phenolic is used.
  • A PCB made up of paper phenolic could easily break in the extreme conditions which a tank will undergo.
  • Hence, for defence purpose PCB’s made up of glass epoxide is used.
  • In this molten glass is mixed with an adhesive (epoxide) along with fibre threads to impart strength.
  • The material formed is pale yellow in colour.
  • To make it green like commercial ones solder masking is used.
  • This kind of PCB has resistance to stress & strain, it also has no EMI or EMC.
  • When the solder masking is used some space is left for soldering.
  • To check whether a particular PCB has been soldered, a coating of Humiseal is used.
  • The Humiseal coating solves two purposes.
  • If we keep the PCB under UV radiation the PCB having soldered joints reflects UV & the other one does not.
  • This coating also saves the PCB from fungus under humid conditions & hence the name humiseal. 



·        In the assembly area the stablizers are assembled.

·        Newton’s 3rd law states that “Every action has an equal and opposite reaction”.

·        If we try and position the barrel of a gun, according to Newton’s 3rd law the gun will take some time to position itself which can be fatal in a war situation. So, stablizers are used.

·        The various parts of a stabilizer are:

1.     K1

2.     K2

3.     Frequency Stablizers

4.     Gun Setting Device

5.     Block Relays

6.     Hydraulic Traverse

7.     Hydraulic Elevation


·        A 26V DC supply from the battery of the tank is converted to 550V, 600Hz AC.

·        It is given to the 2nd distribution unit called K2.

·        K2 is used to protect K1 from surge voltage. It supplies the voltage to K1 and prevents its damage.

·        To regulate the signal from K2, block relays are used & then supply is to K1.

·        When K1 receives AC the relays of K1 are energized & K1 is started.


  • The K1 is the heart of the tank.

  •  It contains two amplifiers.

  • One is for traverse and other is for elevation.

  • This controls the movement of the barrel.

  • To point the barrel in a particular direction the position of the target has to be estimated.

  • For this purpose the velocity and height of the target has to be determined.

  • A laser is pointed to target and with the help of a radar the the height and velocity of the target is determined. Now, the location of the target is known and the barrel can be pointed to it.

  • The Linear Acceleration Transmitter (LAT) helps in maintaining the zero position of the barrel.

  • The height and velocity of the target is determined according to the zero datum line.

  • Derescope is used to convert the mechanical movement of the handle to electrical signal to be sensed by the hydraulic systems.

  • The traverse and elevation signals are then separated and given to the traverse & elevation amplifiers respectively.




Principles of Operation

·        R-174 (MK-II) provides intercommunication between tank crew members and external communication through selected radio channels.

·        The various modes of operation are:

1.      Intercom Mode of Operation:                                                                                                                    In this mode the user is given a communication helmet with two earphones & two throat microphones. When a crew member speaks audio output of 0.8mV is amplified to 0.55V by throat microphone housed in MH1 assembly. Audio output from MH1’s of commander, gunner, driver & external user is fed to intercom amplifier PCB on AC34. The audio signal is summed up and amplified to 10 +/- 2V in ICA PCB. The combined audio output of AC34 is given to the earphones of all users & so communication takes place.


2.      Radio Communication Mode of Operation:                                               Select the mode selection switch of AC34/AC35 to either R/ST1 or R/ST2 or R/ST3. AC34 & AC35 can select any one the three radio sets. 0.55 audio output of MH1 is disconnected from intercommunication amplifier by operation of relays in control PCB of AC34/AC35 & to selected radio stations. The received audio signal from selected radio to respective earphones through control & leak amplifier PCB’s.

3.      Main Control Unit, AC34:                                                                                  It is located at the right of commander. It is used by the commander. All the three radio sets are connected through this this unit. It also interconnects commander to other crew members i.e. gunner device & external user. The mode selection switch of AC34 on front panel enables tank commander to select any modes- Intercom (IC), Radio Stations R/ST1, R/ST2, R/ST3.


  • Control of Front Panel
  1. Volume control adjust audio output of intercom mode
  2. Selection of IC or R/ST1 mode for driver.
  3. Volume control potentiometer with ON/OFF switch for audio leak.
  • Functions of Unit
  1. Amplifies throat microphone signals from communication helmet of all users & feeds to all earphone.
  2. Selection of appropriate radio station signals.
  3. Mixing of audio signals for audio leak purpose.
  4. Generation of special laser warning signal

Sub-Assemblies in AC34

  1. The front panel assembly contains all controls & switch for operation of the system.
  2. Relay control board for control switch operation of Intercom Amplifier board (ICA) where throat microphone output are amplified & fed to earphones.
  3. Power supply filter board, filters out line voltage ripples & spikes and provides supply voltage to all units.
  4. Telephone repeater (TR) leak board, sums main signal with audio leak when audio leak switch is ON. Audio leak is the process when the commander & the gunner can over hear communication of other crew members in addition to his main signal.

4. Operators Switch Unit, AC35:

It is located at the left side of the gunner, for communication. Mode selection switch of AC35 located on top housing enables gunner to select any mode- Intercom (IC), audio stations R/ST1, R/ST2, R/ST3. It has potentiometer controller with ON/OFF switch for controlling audio leak signals from other two radio stations.

  • Sub-Assemblies of AC35:

a)      Controlling board of relays for controlling switching operations.

b)      Leak amplifier board, sums up main signal with audio leak when switched ON.

5. Matching Amplifier Unit AC37:

    It is used by the driver. It has a number of controls depending upon the position of driver’s switch in AC34 as selected by the commander. This unit is connected to intercom or external communication through radio station R/ST1. It has amplifier TIC-3C signal and feeds to ICA PCB assembly.

6. Chest Switch, MH1:

     It has two controls. Ring Knob to bring all to the circular intercom mode. XMTR Knob to enable entry into the radio station transmission.

Tank Intercom System

R-174 (MK-II) is indigenous version of Russian equipment meant for intercommunication between crew members through radio designed for compatability with radio sets R-173 & other CNR, STARS-I, TADIRAN.

  • The following sub units are used for maximum configuration-
  1. Main Control Unit, AC34
  2. Operating Control Unit, AC35
  3. Matching Amplifier Unit, AC37
  4. Line Communication Unit, AC38
  5. Chest Switch, MH1
  6. Interconnecting Cables


1. Internal two way communication between upto 6 users.

2. External two way communication over any 3 radio station of vehicle.

3. Internal circular 2 way communication between all users.

4. Listening to ring tone from radio.

5. Ringing to external user over radio.

6. Magneto ringing to external user, operating over line communication.

7. Facility for selecting/controlling audio leak. **

8. Special audio tone for laser warning signal.

9. Station capability enhanced from 2 ˝  to  3 radio stations. **

**  Additional feature of R-174 (MK-II) over  R-174. 


Technical Specifications

  • Electrical
  1. I/P Power Supply- 27 +2V/-5V
  2. Power consumption- 30W
  3. Frequency Response for 300-3400 Hz.
  4. Distortion- Should not exceed 5%. I/P  &  O/P levels of various section are measured at 1KHz.
  • Physical
  1. AC34: 162 X 143 X 111.5
  2. AC35: 93 X 86 X 89
  3. MH1: 126 X 52 X 32
  4. AC38: 162 X 143 X 111.5
  5. AC37: 68 X 57 X 52

      (in mm)

  • Environmental

As per JSS 55555


As per MIL-461

This battery is used for back up purpose. When we switch ON the tank, due to voltage drop flutuations occur. To prevent this back up battery is used to maintain the voltage supply.

It consists of 20 Ni-Cad batteries each having 1.2V, recharged. It is connected with Turret Distribution Junction Box (TDJB) in which 24V DC tank supply is available. It has 4 output points GMS, GCS, CDS & computer console. One relay having a contact, connected in series with battery. When tank supply is ON the relay is operated & battery is charged by 50A fuse & supply is available at the output points. Stable condition is achieved when there is fall in tank supply & it fulfills the requirement of IFCS. We should avoid discharge of back up battery when tank battery is OFF.


·        Dimension: 315 X 290 X 235 mm ( max )

·        Electrical

1.     Rechargeable Ni-Cad section HEB, TYPE: NC219

2.     Nominal Voltage: 24V

3.     Normal Capacity: 23 AH at 1hr rate, 2.5 AH at 10hr rate.

4.     Number of cells: 20 (connected in series)


  1. Vibration (sinu): 5-13 Hz @ constant displacement of 3mm, 13-300 Hz @ 2g, sweep not exceed one octave/min.
  2. High Temperature: Operation  -55 degree C +/- 3 degree C for 8 hours in switch ON mode.   

Storage: 70 degree C +/- 3 degree C for 8 hrs in OFF mode.

       3.  Low temperature:

Operation:  -20 degree C +/- 3 degree C for 8 hrs in ON.

Storage:  -30 degree C +/- 3 degree C for 8 hrs in OFF.

       4.  Shock: 2 shock of peak acceleration 100g, 6 msec.

  1. Damp Heat:  40 degree C +/- 2 degree C at RH >=95% & duration 16 hrs.
  2. Dust: 40 degree C +/- 2 degree C at RH >=95% & duration 16 hrs.
  3. Bump: 4000 +/- 10 bumps, acceleration of 40g +/- 10%.


·        Relay Holding Time Check:

Connect the unit to DC variable power supply. Keep S1 in closed position. Set voltage to 18V. Connect the I/P & O/P to DSO. Switch on DC power supply and open S1. Monitor I/P & O/P waveforms on DSO & check time delay between them. It should be >=400 msec.

·        Checking of Resettable Fuse:

Disconnect the I/P power supply. Pull the reset fuse out. Check the battery voltage at monitoring socket. It should be 0V. Push fuse in & measure voltage. It should be 24V.

·        Battery Charged Condition Check:

Pull the resettable fuse out & connect the monitoring socket terminals S1, (+ve) to A or B of X1, S2 (-ve) to F or G of X1 by a shorting link. Connect a resistive load across A & B and F & G of output connector X2. Now, push the fuse in. Battery is discharged at 23A & to an end voltage of 20V & the duration of discharge not < 60 min for a fully charged battery.

List of Instruments

1.      Vernier Caliper 150 mm

2.      Vernier Caliper dial 200 mm, CD Vernier Caliper 200 mm

3.      Vernier Caliper dial 150 mm

4.      Vernier Caliper digital 150 mm

5.      Threaded Ring Gauges

6.      Thread Plug Gauges

7.      Measuring Tape 7.62 meters, Measuring Tape 3 meters

8.      Plain Plug Gauges 1.00 to 2.00 mm

9.      Bevel Protractor

10.  Thread Plug Gauges

11.  Limit Switch Fixture

12.  Microscope

13.  Steel Ruler 60 mm, Vernier 400 mm

14.  ‘U’ Clamp

15.  Plain Plug Gauges 10.00 mm to 12.00 mm

16.  Plain Plug Gauge 4.01 mm to 6.00 mm

17.  Plain Plug Gauge 1.00 mm to 2.00 mm, 2.01 mm to 4.00 mm, 4.01 mm  to 5.00 mm, 8.01 mm to 10.00 mm

18.  Micro Meter Stand

19.  Micrometer Digital

20.  Micrometer low force

21.  Delta Scope, Iso Scope

22.  Micrometer pin

23.  Micrometer flange

24.  Micrometers

25.  Combination Set Square

26.  Plain Plug Gauges 2.05 to 10.00 mm

27.  Vernier Caliper loop

28.  Plain Plug Gauge 8.01 to 10.00 mm, 1.00 to 2.00 mm,2.05 to 10.00 mm, 6.01 to 10.00 mm



·        Plan and execute the project.

·        Study of engineering drawing.

·        Clarification of drawing.

·        Make or buy decision (Purchase & Sub-contract)

·        List of Materials (bill)

·        Procurement of Scheme- till dispatch

 Instruments Calibrated

  1. Digital Multimeter
  2. Oscilloscope
  3. Function Generator
  4. Distortion & Audio Analyzer
  5. Power Supply
  6. Thermometer
  7. Break down Tester
  8. High Resistance Meter
  9. Frequency Counter
  10. XY Graphic Recorder
  11. Power Meter
  12. Synchronous Meter
  13. Resolver Meter
  14. Dynamic Signal Analyzer
  15. Control System Analyzer
  16. Spectrum Analyzer


It gives me immense pleasure to write that my practical training was completed successfully. I hope this unique opportunity provided to me by The University of Rajasthan, Jaipur will in future help me in gelling with my colleagues & doing team work. I also learned to abide by the rules and regulations of industries & how to  present myself towards my seniors. I hope I can help my country in the near future to go ahead of other countries and develop.



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