TRAINING PRESENTATIONBHARAT SANCHAR NIGAM LIMITED

• Bharat Sanchar Nigam Ltd. was incorporated on 15th September2000.

• BSNL has installed Quality Telecom Network in the country & nowfocusing on improving it, expanding the network, introducing newtelecom services with Information Communication Technologyapplications in villages & winning customer's confidence.

• Today it has about• 43.74 million line basic telephone capacity.

• 8.83 million WLL capacity

• 72.60 million GSM capacity

• 37,885 fixed exchanges

• 68,162 GSM BTSs (Base Transmitting Stations)

• 12,071 CDMA Towers

• 197 Satellite Stations

Connecting 623 districts, 7330 cities/towns & 5.8 lakhs villages through microwave andoptical fiber.

• Power plant consists of diesel generators, inverters,batteries.

• Telephone Exchange deals with landline, mobile,wireless landline.

• Broad Band deals with the high speed internet accessthrough wire and wireless. Wimax is a new technologyfor internet access wirelessly.

• Media Room is the heart of any telephone exchangebecause all data whether voice, video, text,multimedia, etc. all are transmitted and received hereonly.

• The Primary requirement of any Telephone System is that service shall

be available to the subscriber at all times.

• The electrical energy required for signaling, switching, speech

transmission etc. in telephone exchange is derived either directly or

indirectly from the public supply.

• In order to provide uninterrupted service, the exchange power supply

system is designed to give continuous energy to the system. So

provision is also made for alternate source of supply in the event of

mains failure or public supply failure.

• The Emergency Energy is derived from

1. Batteries

2. Generators

• Generally the lead acid type secondary cells are used.

• Secondary cells are electrolytic cells for generation of electric energy.

• These cells can be restored to its original condition by passing acurrent in opposite direction to the flow of current in the cell duringthe discharge.

• Harmonics of A.C. may affect the speech signals.

• Relays used in telecom systems are more sensitive to D.C than A.C.

• Transistors and I.C.s etc. being unidirectional devices, the use of D.C

has become necessary.

• Arranging standby source to A.C is difficult compare to D.C because

secondary cells can be used as Standby source.

NEED OF D.C. POWER SUPPLY

• SMPS is an equipment, which gives uninterrupted DC power supply to the

telecommunication systems.

• The power system is intended primarily to provide uninterrupted DC power

to Telecom equipment and current for charging the batteries in the presence

of AC Mains.

• The system works from commercial AC mains which is rectified and

regulated to -50V, -48V, -5V, etc. DC and is fed to the equipment

(exchange).

SWITCH MODE POWER SUPPLY (SMPS)

• Here two sets of batteries (24 cells each set) are connected in parallel

to the output of the rectifier for charging.

• Each Battery is about 2 V.

• The output of the rectifier is 51.5 V. Hence floating voltage of each

cell is 51.5 divided by 24 = 2.15V/ cell.

SWITCH MODE POWER SUPPLY (SMPS)

BATTERY ARRANGEMENT AND WORKING

Each Battery is connected in series to make 24V

and there are two sets of 24V battery.

SMPSAC INPUT

DC LOAD

24V BATTERY

24V BATTERY

• Another major problem with SMPS power supplies is that they

generate very large amount of radio frequency interference as well as

disturbance on its output bus, due to the high switching frequency used

at the various internal stages.

• This problem can be reduced through the use of properly designed

additional RFI filters at both its input and output.

SWITCH MODE POWER SUPPLY (SMPS)

FUNCTIONAL BLOCK DIAGRAM OF SMPS

AC InputRFI and EMI SuppressorAC Filter

RectifierFilter Capacitor

BankDC to DC Converter

Ferrite Core or Metglas

Transformer

High Speed Rectifier

FilterEMI and RFI Suppressor

DC Output

Toroid Ferrite Core EMI/RFI Suppressor

• These compact sized Toroid Ferrite cores are useful for suppressing EMI/RFI.

• A tough epoxy conformal coating helps reduce breakage.

Metglas Transformer

• An amorphous metal (also known metallic glass or glassy metal) is a solid metallic material, usually an alloy, with a disordered atomic-scale structure.

• It exhibits very low loss at higher frequencies.

• DC To DC Converter

• Produces a chopped train of unidirectional flat topped pulses.

• Produces an alternating waveform with flat-topped pulses.

• Ferrite Core Transformer

• The unidirectional or alternating pulses generated by the converter stage is fed to

it because it can handle these waveform and transform them at the secondary

winding to a different magnitude in voltage.

• Thus the high voltage pulses are reduced to a smaller magnitude.

• High Speed Rectifier

• The alternating waveform is rectified by a high frequency compatible rectifier

stage using either a bridge or center tap full wave configuration.

• Even if the transformer output is unidirectional, a blocking rectifier stage is

essential at the output to prevent reverse polarity waveform generated by the

transformer calling flux ( at the end of the pulse ) from the reaching the output

• To provide an earth connection to the battery circuit, to stabilize the potential of

the lines and equipment with respect to earth.

• Enabling single pole switching,reduces the number of fuses required in the circuit.

• To provide protection to persons and plant against leakage from station power

wiring to metallic apparatus, frames etc.

• To provide means of earthing electrostatic screen on apparatus and of earthing

lead sheaths of cables.

• To complete the circuit of telephone systems employing a common path for

signaling purposes.

EARTHING IN TELEPHONE EXCHANGE

• In electrolysis positive electrode will be normally corroded. If we keep our lines

and equipment at negative potential, we can minimize troubles from the corrosive

effects.

• If positive voltage is there in the line then tapping could lead to run a motor, light

a bulb, can be used to charge a battery, etc.

• Partial Earth faults can be definitely identified if the conductor is negative.

Otherwise fault is liable to seal up owing to oxidation.

REASONS FOR GROUNDING POSITIVE POLE OF D.C

• It is used as an emergency power-

supply.

• Daily Consumption on an average is

about 100 liters of diesel for 250 KVA.

The main purpose is to meet the

demand of Network towers, OCB

(Optically Controlled Birefringence),

Air Conditioners for cooling the

equipment for about 24 hours.

DIESEL GEN SET

• All types of data whether voice, text, video, multimedia, etc. is converted,

transmitted, received, multiplexed, DE multiplexed here.

• Conversion from one form to another

1. Electrical

2. Micro Wave

3. Optical

From the media room and to the media room the data is carried mainly by optical fiber.

• Optical Fiber is a new medium, in which information (Voice, Data or Video) is

transmitted through a glass or plastic fiber, in the form of light, following the

transmission sequence give below:

FIBER OPTIC SYSTEM

• Telecommunication applications are widespread, ranging from global networks to

desktop computers.

• Transmission of voice, data, or video over distances of less than a meter to

hundreds of kilometers.

• Secure and Reliable.

• The high bandwidth provided by fiber makes it the perfect choice for transmitting

broadband signals, such as high-definition television (HDTV) telecasts.

FIBER OPTIC APPLICATIONS

• Intelligent transportation systems, such as smart highways with intelligent traffic

lights, automated tollbooths, and changeable message signs, also use fiber-optic-

based telemetry systems.

• Fiber-optic systems are used in most modern telemedicine devices for

transmission of digital diagnostic images

• Other applications for optical fiber include space, military, automotive, and the

industrial sector.

FIBER OPTIC APPLICATIONS

• Speed: Fiber Optic operates at higher speed up to Gbps (Gigabytes Per Second).

• Bandwidth: Theoretically infinite bandwidth.

• Distance: Signals can be transmitted further without needing to be "refreshed" or

strengthened.

• Resistance: Greater resistance to electromagnetic noise such as radios, motors or

other nearby cables.

• Maintenance: Fiber optic cables costs much but cost less to maintain.

ADVANTAGES OF FIBER OPTICS

FIBER TYPES

FIBER COMMON CONNECTOR TYPES

OPTICAL FIBER

PARAMETERS

Window

Wavelength

Frequency

Dispersion

Attenuation

Bandwidth

OPTICAL FIBER SPLICING

Splicing means creating a

permanent joint between two fibers.

• The slightest scratch, mark or

actually speck of grime may

influence the transmitting of

light.

• It could slice in our skin without

being observed by the human

eye.

OPTICAL FIBER SPLICING

Types of Splicing

Glue splicing.

MechanicalFusion splicing

MECHANICAL SPLICING

FUSION SPLICING

• The telephone is a telecommunication device that is used to transmit and

receive electronically or digitally encoded speech between two or more

people conversing.

• Telecommunication networks carry information signals among a facsimile

machine, a tele printer, a data terminal.

• NEED FOR PCM

• To cater to the increased demand of traffic between two stations or same

station.

• Increasing number of pairs to the under ground cable is uneconomical and

leads to maintenance problems.

• MULTIPLEXING

• The technique used to provide a number of circuits using a single transmission link is called

Multiplexing.

PULSE CODE MODULATION

• NEED FOR PCM

• To cater to the increased demand of traffic between two stations or same

station.

• Increasing number of pairs to the under ground cable is uneconomical and

leads to maintenance problems.

• MULTIPLEXING

• The technique used to provide a number of circuits using a single transmission link is called

Multiplexing.

PULSE CODE MODULATION

• TIME DIVISION MULTIPLEXING

• Sharing a transmission medium by a number of

circuits in time domain.

• Establishing a sequence of time slots during which

individual channels (circuits) can be transmitted.

• Entire bandwidth is available to each channel.

• Each channel is assigned a time slot with a specific

common repetition period called a frame interval

• Each channel is sampled at a specified rate and

transmitted for a fixed duration.

MULTIPLEXING TECHNIQUES

• FREQUENCY DIVISION MULTIPLEXING

• Process of translating individual speech circuits (300-

3400 Hz) into pre-assigned frequency slots within the

bandwidth of transmission medium.

• Translation is done by Amplitude Modulation of the

audio frequency with an appropriate carrier frequency.

• At the output of the modulator a filter network is

connected to select either a lower or upper side band.

• Its application is in the analogue transmission

systems.

MULTIPLEXING TECHNIQUES

• 125 microseconds are divided into 32 parts (Time Slots).

• 30 Time Slots are used for 30 speech channels.

• One time slot for signaling & one time slot for synchronization.

• Time available per channel would be 125 / 32=3.9 μ seconds.

• Time period of sampling or the interval between two consecutive samples of

a channel is 125 μsec. This duration is called TIME FRAME.

30 CHL PCM SYSTEM

• A Typical Telephone Exchange -OCB-283

• It is made up of three independent functional units.

• The “Subscriber Access Subsystem” which carries out connection of analogue and

digital subscriber lines.

• “Connection and Control” which carries out connections and processing of calls.

• “Operation and Maintenance” which is responsible for all functions needed by the

network operating authority.

ALCATEL E10 (Optically Controlled Birefringence, OCB)

DEVELOPMENT OF EXCHANGES

• With the introduction of PCM (Pulse Code Modulation) technology in the 1960s,

communications networks were gradually converted to digital technology over the

next few years.

• To cope with the demand for ever higher bit rates, a multiplex hierarchy called the

Plesiochronous Digital Hierarchies (PDH) evolved.

• International Telecommunication Union (ITU), it coordinates standards for

telecommunications.

• Then Synchronous Digital Hierarchy (SDH) was developed by ITU.

OPTICAL FIBER TRANSMISSION SYSTEMS

• Synchronous Digital Hierarchy (SDH)

are standardized protocols that transfer

multiple digital bit streams synchronously

over optical fiber using lasers or highly

coherent light from light-emitting diodes

(LEDs).

• For transporting large amounts of

telephone calls and data traffic over the

same fiber without synchronization

problems.

SYNCHRONOUS DIGITAL HIERARCHY (SDH)

• SDH is a transport hierarchy based on multiples of 155.52 Mbit/s. The basic unit

of SDH is STM-1 (Synchronous Transport Module).

• Different SDH rates are:

• STM-1 = 155.520 Mbit/s

• STM-4 = 622.080 Mbit/s

• STM-16 = 2,488.320 Mbit/s (~2.5 Gbit/s)

• STM-64 = 9,953.280 Mbit/s (~10 Gbit/s)

• The STM-4 specification is designed to carry 7,680 8-bit "voice" frames every 125

micro-seconds for a total payload bit rate of 491.520 Mbit/s.

SYNCHRONOUS DIGITAL HIERARCHY (SDH)

SCHEMATIC DIAGRAM OF HYBRID COMMUNICATION NETWORKS

ATM : Asynchronous Transfer Mode

ADM : Add Drop Multiplexer

DXC : Digital Cross Connect

TM : Terminal Multiplexer

• WiMAX (Worldwide Interoperability for

Microwave Access) is a wireless

communications standard designed to

provide 30 to 40 megabit-per-second data

rates, with the 2011 update providing up to

1 Gbit/s for fixed stations.

• FTTH (Fiber to the Home):

• Fastest Speed Achieved by this network.

• In Gbps speed.

EMERGING TECHNOLOGIES