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When I have nothing else to do, I pick up the phone and dial some phone number. Not any random number, mind you. I dial, for example, +971 2 213793. This was my phone number when I was staying in Abu Dhabi, U. A. E. It no longer exists and I learnt of the various internationally accepted tones to indicate "Number Unobtainable" status. Once I dialled +1 301 491 6264. It turned out this was the number of a cellular phone using the service of "US Cellular", a cellular operator in the USA. It was then that I realised that in the US, all communication devices, have numbers with the same number of digits, irrespective of whether they are land-line phones, cellular phones, pagers, or fax-machines. There are so many other things that I discovered similarly. And I didn't embark on my voyage of discovery just by dialling international numbers alone. I have gleaned a wealth of information by dialling local phone numbers too.
In the links that follow, I have listed many of the things I learnt playing around with the device that is a member of virtually every household in the world today. I have also explained how I arrived at my conclusions.
Before you go on, there is something you must first know. The telephone exchanges that are in use around the world are not made by one single manufacturer. All telephone operators buy switching equipment from a variety of vendors. I have listed some companies that design and manufacture exchanges, along with the names that the exchanges go by. By far, these are exchanges in use in India, but most of them are also used in other parts of the world. Goes to show that India's telecomm infrastructure is truly world-class.
They make 3 exchanges that I know of. One is the E10B, also called the OCB-181. The E10B is one of the earliest SPC digital exchanges in the world. They were commissioned first in France sometime in the mid-eighties. One of the best moves the Indian Telephone Industries ( a Government-owned company ) did was to enter into an agreement whereby the E10B was manufactured under license by the ITI in India. E10Bs started entering service all over India by 1989-1990. In fact, the telephone exchange to which I'm connected is an E10B, one of the first to enter service in Madras in 1990. The E10Bs were deployed in huge numbers all over India to such an extent that a separate wing of the Department of Telecommunications was created to provide service and maintenance for the E10B installations. This wing is called the National Centre for Electronic Switching.The NCES has a website.
The second switch made by Alcatel is the OCB-283, also called just the OCB. The OCB-283 is the sucessor to the E10B, and is called the 1000 E10, or just E10. The OCB is also manufactured by ITI under license, just like the E10B. In fact, I don't think ITI manufactures the E10B any more. All installations of the E10B are being replaced by the OCB, and I think my E10B will soon be replaced by the OCB. The OCBs account for a major portion of the landline network of the Government-owned Department of Telecommunications (DoT) in India today, at least the end-offices ( exchanges directly serving customers ). The OCB is better than the E10B in that it simply packs more punch for today's advanced services, and for tomorrow's too. It supports SS7 and therefore is ISDN-ready. It has a fast signalling processor, which makes call setup time much lesser. The OCB is the preferred choice in the DoT for ISDN installations. On a minor note, the ITU refers to the OCB283 as the E10. Click here for the page from the ITU site.
The third switch is the System 12. But the System 12 was originally designed by another company that was later bought by Alcatel.
The AXE10 is Ericsson's best-selling switch, and all over the world, the AXE10 is synonymous with performance and quality. The AXE10 is a fantastic switch that is used in more countries and networks than any other switch, and is used in a variety of configurations. It is the switch with just about the fastest processor that I've seen, and that is a fact that I have confirmed. There are a lot of AXE10 installations in India, but I know the AXE10 better as an International Gateway Exchange. The VSNL ( Videsh Sanchar Nigam Limited ), a Government-owned company that has a monopoly on international telecommunications traffic from and to India ( until 2001 ) has AXE10s handling all of the international telephone traffic. I have visited VSNL in Madras, and seen the AXE10 in service there as a Gateway Digital Swithing System. The AXE10 is also one of the most used switches by cellular operators in India - almost 40% of the cellular network in India is centred around an AXE switch. In the U.K., the AXE10 is called System Y ( you'll realise why as you read on ! ) and is used prominently in the British Telecom network, and also by Vodafone, a cellular operator. The AXE10 is my choice for the best switch in the world.
I only know of one switch made by Siemens - the EWSD. EWSD is a german acronym and I don't quite remember the expansion. The EWSD is a fast switch that has a lot of worldwide installations. But I haven't heard of the EWSD in installations other than subscriber installations. In fact, in the DoT network, all EWSD installations are just subscriber installations.
There are two switches I have heard of. I still don't know if they are both configurations of the same basic switch. The DX200 is one of them. The other is the DX220. The local cellular provider in Madras, Skycell, has a system with a Nokia DX200 switch.
GEC Plessey Telecommunications - GPT ( England )
The Post Office / Telephones Authority in the U.K., along with GPT, designed the System X, an all-British digital SPC exchange. System X has extensive installations in the UK network of British Telecom along with the AXE10 ( which is called System Y 'just to make things simple' ). I don't know of System X installations anywhere else. System X, even in the UK, is mostly used to server subscribers and as transit / tandem exchanges. International gateway exchanges in England ( International Switching Centres, as they are called ) are usually AXE10 ( Madley and Keybridge in the UK are ISCs with AXE10s ), and I don't know of any System X ISC.
Lucent - AT&T Bell Labs ( U. S. A. )
I know of two switches that is made by Lucent. One is the 4ESS. The ESS stands for Electronic Switching System. The 4ESS is the heart of the trunk network in the USA. It is one BIG switch. In full capacity, it can handle upto 107,000 circuits. There is simply no other switch today that can match the 4ESS in sheer size.
The latest generation switch from Lucent is the 5ESS, and is widely used in the American telephone network. It is the only serious competition to the AXE10, at least in the US. The 5ESS, unlike the AXE10, has a centralized ( non-modular ) design. There is a variant of the 5ESS called the 5ESS-PRX manufactured by Lucent in collaboration with Phillips Communications of Holland. It is merely a customised 5ESS for particular markets. The DoT in India has 5ESS installations, and I know of many subscriber installations. ISCs in England also use the 5ESS.
Nortel is famous for the switches, the DMS100 and the DMS250. These switches are also widely used in the North American network. One ISC in England is a DMS100 installation. The DMS switches are used also by many cellular operators in the US and elsewhere.
Fujitsu makes the Fetex range of switches. There are three installations of the Fetex in Madras, but these are electronic SPC non-digital exchanges and will soon be replaced by digital switches. I do not know of any other Fujitsu installations.
The new generation ISDN switches from Fujitsu are also called Fetex switches.
NEC - Nippon Electric Corporation ( Japan )
The NEAX family of switches are manufactured by NEC. Similar to the Fetex, there are analog electronic NEAX installations in India. The NEAX61 is a digital switch from NEC. The NEAX61 is manufactured in India under collaboration, and is used in rural/semi-urban areas.
C-DOT Centre for Development of Telematics ( India )
The RAX ( Rural
Automatic Exchange ) and the MAX ( Main Automatic Exchange
) are indigenously developed SPC digital exchanges from the C-DOT, an organisation
under the DoT. The RAX-128 with 128 ports is used all over India in rural
areas, and is better suited for the harsh climatic conditions, where the
other exchanges from Alcatel and Ericsson fail to perform. The Multiple
Base Module MAX has been certified by the ITU and is being exported to
many countries.
Indian National Numbering Plan
List of exchanges in Madras with exchange code ( first 3 digits of the subscriber's number )
My collection of PSTN ring tones and other tones
Trunk Automatic Exchanges connecting Madras to the outside world
Information about the cellular operators in Madras
manisridhar at hotmail dot com
