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Author Topic: BT NTE 4U/7A  (Read 892 times)

daddum61

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BT NTE 4U/7A
« on: September 18, 2018, 12:37:51 PM »

I have to do some work on an old site that has this BT NTE installed, but i can find no info anywhere on the NTE
They are using it for pure comms (IP based) not telephony.
Currently the connection to the unit is by 4 serial links that look like they are running at 2meg
however the old router that connected to the NTE has died so i am replacing it with a new cisco router

I think the NTE interface is x21 but not sure if it is DTE or DCE, however i note that there is an rj45 socket next to each serial(x21) port on the NTE

does anyone know if i can just connect using ethernet rather than serial cables ?
there are some dip switches on the unit but i have no idea what they do
thanks in advance
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dee.jay

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Re: BT NTE 4U/7A
« Reply #1 on: September 18, 2018, 02:33:36 PM »

What are these circuits doing? X.21 is very old now!

What was the old router that was connected to the NTE?
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burakkucat

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Re: BT NTE 4U/7A
« Reply #2 on: September 18, 2018, 09:40:20 PM »

Ah, an Access Synchronous Digital Hierarchy NTE 4U/7A.  :)

You might like to review one of my old threads.

The network connection, via the optical fibre, is to the SDH in BT-land. The NTE can support four individual access connections. (The four TRIBs.)

Each tributary can accept a connection via one of the following methods --
  • BNC connectors, unbalanced, 75 Ohm
  • Modular 8P8C connectors, balanced, 120 Ohm
  • X21 serial, 15-pin D, DCE

. . . the old router that connected to the NTE has died so i am replacing it with a new cisco router

I think the NTE interface is x21 but not sure if it is DTE or DCE, however i note that there is an rj45 socket next to each serial(x21) port on the NTE

Those modular 8P8C sockets are not Ethernet interfaces but 120 Ohm balanced interfaces, so you will have no success in connecting a device that expects Ethernet signals.

Please describe the "old router" that has died (make & model) and how it was connected to the ADSH unit. What Cisco router are you thinking of using?

How many of the tributaries are in use?
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daddum61

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Re: BT NTE 4U/7A
« Reply #3 on: September 19, 2018, 03:42:29 PM »

the old router is a DEC RouteAbout Central !

i was going to use a cisco CAB-SS-X21-MT to connect from my cisco serial WIC to the NTE
this cable is described as DTE so should i get the CAB-SS-X21-FC ?
this is described as DCE but it is the wrong gender I think for the NTE
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burakkucat

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Re: BT NTE 4U/7A
« Reply #4 on: September 19, 2018, 03:53:33 PM »

the old router is a DEC RouteAbout Central !

So rather elderly.  :o

Quote
i was going to use a cisco CAB-SS-X21-MT to connect from my cisco serial WIC to the NTE
this cable is described as DTE so should i get the CAB-SS-X21-FC ?
this is described as DCE but it is the wrong gender I think for the NTE

To the best of my knowledge, the X21 ports of the ASDH NTE 4U/7A are classified as DCE. If documentation can be found for the DEC RouteAbout Central, perhaps that might clarify the situation.  :-\
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daddum61

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Re: BT NTE 4U/7A
« Reply #5 on: September 19, 2018, 04:12:13 PM »

what little info i can find implies that the DEC kit is DTE

so is a cisco DTE cable designed to connect to a DTE interface or is it presenting as a DTE connection i.e. designed to connect to a DCE interface ?
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burakkucat

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Re: BT NTE 4U/7A
« Reply #6 on: September 19, 2018, 04:21:17 PM »

I really can't help you with Cisco cables . . . they are in a class of their own.  :-X

However, with your belief that the DEC kit's interface presents as DTE and my belief that the 4U/7A presents as DCE, the cable required is a straightforward one to one mapping. One end with a male plug, the other with a female plug and all 15 pins connected straight through.

 1 -  1
 2 -  2
 3 -  3
 <etc>
13 - 13
14 - 14
15 - 15
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daddum61

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Re: BT NTE 4U/7A
« Reply #7 on: September 19, 2018, 04:45:08 PM »

i think the service on site is
https://www.btplc.com/SINet/SINs/pdf/223v3p3.pdf

see section 4.3.1

i suspect i will just end up connecting a cable ans see if the cisco box picks up the clock from the NTE
they have 4 of these old DEC things along with their DEC servers that keep a big part of london ticking
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burakkucat

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Re: BT NTE 4U/7A
« Reply #8 on: September 19, 2018, 05:02:20 PM »

i think the service on site is
https://www.btplc.com/SINet/SINs/pdf/223v3p3.pdf

see section 4.3.1

Yes, MegaStream 2, that seems to be it.

Quote
i suspect i will just end up connecting a cable ans see if the cisco box picks up the clock from the NTE

That would be a reasonable experiment.
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