Trunk Automatic Exchanges and Tandem switches in Madras
Tandems help connect pairs of switches that are not directly connected.
Inter-city switches are called trunk automatic exchanges ( TAX ). For example,
a TAX in Madras with a connection to a switch in Bombay, would indirectly
connect all the switches in Madras ( connected to this tandem ) to Bombay.
There are 4 TAXs that I know for sure are there in Madras. They are
.....
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Flower Bazaar TAX/Tandem - I think it's a 5ESS tandem.
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K. K. Nagar Tandem -it's an Alcatel OCB283. This OCB runs software release
R23 and is also a Signal Transfer Point ( STP ) in the SS7 network.
-
Anna Road ( Mount Road ) Tandem
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The Haddows Road TAX - this is one very important installation in Madras.
Haddows Road ( Nungambakkam ) has a huge chunk of transmission links coming
into and going out of Madras to other places. There is a long-distance
digital microwave link to Bombay, among other things. I happened to visit
a repeater station for this link near Mysore at a place called Chamundi
Hill. Haddows Road also houses a Network Management Centre.
All of these tandems have trunks connected to the local VSNL international
tandem switch, called the Gateway Digital Switch. While all the four tandems
route incoming international calls, all international calls from Madras
seem to be routed only through the Haddows Road TAX to the VSNL international
switch. How do I know this ? I happened to visit VSNL some time back, and
picked up a print-out of daily traffic statistics at the VSNL Gateway switch.
The print-out clearly identified Local/Metro trunks leading to the above
4 TAX installations of the DoT.
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