15-01-2013, 04:47 PM
BHARAT SANCHAR NIGAM LIMITED: BSNL
1BHARAT SANCHAR.docx (Size: 424.46 KB / Downloads: 71)
ABOUT THE COMPANY
“BHARAT SANCHAR NIGAM LIMITED” is abbreviated as BSNL. It is fourth largest department of Telecommunication Company in Asia and seventh in world today. Which is one of the most earning revenue in India? Above more than 3 laces employees, officer and engineers working in BSNL at present. Previously electro mechanically exchanges for use in India namely stronger type exchange, cross bar exchange were there. These manual telephone exchanges suffered from some disadvantages. To overcome this automatic exchange was introduced in this system.
In 1980’s PITHROTHA LTD. Introduced “C-DOT” exchange in India. These exchanges replaced by electro mechanical exchange. These exchanges which have wide range of capacity replaced electromechanical exchange, C-DOT-128, C-DOT-256, C-DOT-512, C-DOT-1024(SBM) exchange, C-DOT-2048(MBM) exchange and so on.
Besides C-DOT exchange ILT exchange, E-10B exchange also proved of mild stone in Telecommunication Sector to replace electromechanical exchanges, which were most sophisticated and modern latest techniques electronics exchanges.
There after it was OCB-283 exchange which proved very important exchange in this series to replace electro mechanical exchanges. Now it is “WLL” & “GSM” mobiles which is also proved a mild stone in Telecommunication sector. It was 31st march 2002 when BSNL started these GSM mobile and today it has provided almost 35 lacks mobiles in all over country. WLL system which is also a mobile with limited mobility in city & can have Tele communication facility in that area almost. While GSM can cover all cities of the country.
ELECTRONIC EXCHANGE
Ever since the invention of telephone by Alexander Bell in 1876, the endeavour for improvement in the telecom technology has not found a halt, well to the delight of people in general and to user in particular in pursuit of making and advancement on the on speed, accuracy, quality and cost. We have reach from simple magnets manual system to complex electronic auto system of working.
While the basic principle has not change size, hesitation, efficiency and usefulness have changed to great extent.
BASIC CONCEPT OF TELEPHONE EXCHANGE
In an electronic exchange a computer is used to control the functions of the exchange according to information fed to it through dial pulses by the subscriber.
It is comprised of mainly four sub systems:
1. Terminal Equipment
2. Switching Network
3. Common Control Equipment
4. Input/output Peripherals
THE STANDARD TONE IS:
• DIAL TONE
A continuous low-pitched tone when the handset is lifted to indicate that the telephone is connected to a free selected and that dealing may commence. If the subscriber deal before the selector is ready to receive the pulses, a wrong number or a "no progress" calls result. The tone stops when the first digit is dialed. Although the dialed tone has a fundamental frequency of 33-113c\s, it is rich in harmonic, and most of the sound energy is actually of a higher frequency, this is necessary since the response of both telephone receivers and ear to 33-113 c\s is very low and a pure tone of this frequency would be inaudible to many people.
• RING TONE
An interrupted high-pitched tone heard after dialling is completed to indicate that the call has proceeded satisfactory and that ringing conditions have been set up. The tone stops when the called subscriber answers. The tone is of 400 cycle's frequency and is 0.4 sec on 0.2 sec off, 0.4 sec on 2 second off.
• BUSY TONE
An interrupted pitched tone of 400c\s frequency indicates that the connection cannot be made immediately, but may be attempted again later. When heard before or during dialling busy tone indicates that the connecting switching, are engaged on other calls. When heard after the complete number is dialled it indicates that the subscriber is engaged
OCB- 283 DIGITAL SWITCHING SYSTEMS
All new technology-switching systems are based on stored program control concept. The call processing programs are distributed over different control organs of the system and are stored in ROM/RAM of the units data required to handle the calls are also managed in the RAMs of different control units. Processors in the control units by using the program and data stored in unit ROM/RAM process and handle calls. Handling or processing a call means to ultimately establish a connection in a switch between I/C & O/G ends. Depending on the system the name & architecture of control units and switch may change but basic criterion for switching remains more or less the same.
OVERVIEW OF OCB 283 DIGITAL ELECTRONIC SYSTEMS
OCB 283 is digital switching system which supports a variety of communication needs like basic telephony, ISDN, interface to mobile communication, data communication etc., This system has been developed by CIT ALCATEL of France and therefore has many similarities to its predecessor E-10B (also known as OCB 181 in France).
The first OCB 283 exchanges of r11 version were commissioned in Brest (France) and Beijing (China) in 1991. The first OCB 283 exchanges came to India in 1993. Subsequently, the system has been upgraded and current version R-20 was fully validated in January 1994. The exchanges, which are being supplied to India, belong to R-20 version. At present R-24 versions are also being supplied.