ISDN terminal across 150m - passive S-bus how to?

[mimmas]

Hi to all in this forum
First of all i'd like to state that this is my first experience with ISDN.
The situation is as follows:
=1NT
=1TE in the same room
=1TE on 150m distance - in another building
If i connect the first terminal(PCI card) only - it works
If I connect the other terminal(PCI card) only - it works
The two together - not a chance ... neither of them...

As I remember from the university I have to set up a passive S-bus between the buildings and to connect the NT and the 2 TE to it. it was something about 100 ohm resistors on the 2 sides of the bus. But can somebody be more spesific how to put the load on which wires and so on..

10x in addvance
Best regards
Martin

 

[SL1User]

From my point of view 100m is the max. distance from the last TE to the NT in case of multiple TE's.

About 1000m is the max. in case of an single TE (extended passive bus).

In your case reflexions are screwing up the whole bus.

In the NT there must be a dip setting for the resistors on the other side just but one in the transmit pair and the other on in the receive pair. In case of RJ45 connectors its PIN 4 and 5 and PIN 3 and 6.

Good luck

 

[chris13]

Yes, the extened passive bus is good for distances up to 800m-1100m., depending on the capacity (nF) of the cable.
This config even allows multiple TEs. The trick is, that the 1st(!) and all following TEs have to be on the last(!) 30-50m of the full length. Your 1st TE within the same room as the NT is the problem: distance too low... crazy world

But even the usual short passive bus can cover 120-180m. Make shure the termination is fine, SL1User already posted the details.

The NTs I know have 2 RJ45 sockets. Did you try to plug the first TE directly into the NT?

And you might try to put the NT in the "middle" of the bus, between the TEs. Then both ends (sockets of the TEs) have to be terminated with resistors and the internal termination of the NT has to be disabled.
In europe the NTs sometimes have a small cover under which they hide additional contacts for 4 single wires. These may be used to connect the "second half" of the bus.

In your case it might be just the termination. And what type of cable are you using?

Good luck,
Chris

 

[mimmas]

10x for the fast responce,
i've found the dips that SL1User mentioned. they are set to 100 ohm and as far as i understand this way i'm using the NT as a TR(or termination) and put other 2x100ohm on the other end. The cable between the buildings is STP. Actually there are 2 RJ45 sockets and I'm using them both - one for the stp that connects the distant TE and the other for the TE in the room. Do you think that I have to move the near TE on the S-bus and stop using the second socket if I do the things mentioned earlier.
Is there a connection between these 2 socket, cause if they are separate from one another i guess i can switch the dip on the NT to point-to-point(if this setting works for the separate sockets- thus having 2 point-to-point devices on 2 sockets).(sounds stupid as i read it now )
I can't move the NT cause the cabling between the building is underground, and making changes involves destroying some pavement. NT is some siemens stuff.

I'll try what SL1User suggests using the 2 sockets and will post the results.
Best regard,
Martin

 

[chris13]

It sounds like you've been using the 2 sockets from the beginning on ;-)
ISDN is a robust technology. You may play with the termination without destroing anything.
Disable the internal termination of the NT and try it out.
If it doesn't work, try applying termination resistors to the RJ45-socket in the same room. If it works now, you've put the NT in the middle of a short passive bus with covers one very short and one very long distance...
Hmpf, good question. I've been doing and supporting ISDN installations since 1993, but not during the last 3 years and I don't remember if the 2 sockets of the NT are usually separated or not. I need some vitamines
And now to something completely different:
Do your buildings have a common grounding?
Where is your ISDN coming from, is the U-interface provieded by a carrier or a local PBX?
Perhaps you can "order" a 2nd ISDN-trunk/-line, use 2 wires of the long cable and place the additional NT in the distant building. If nothing helps, perhaps

http://www.blackbox.com

has ISDN-over-LAN adapters.
Let us know what you find out before you begin to destroy the pavements...

Best regards,
Chris

 

[ISDNman]

The idea of moving the NT1 to a point between the two devices is a good one.

The "Short Multipoint" configuration comes close to you needs:

N ------------(400 feet max)--TR(50 Ohms)--(33 feet max)-- TE #1
T
1 ------------(400 feet max)--TR(50 Ohms)--(33 feet max)-- TE #2

In this case the NT1's built-in termination should be set to "off" and both legs should be terminated.

I hope this helps

Good Luck



On all the NT1's I have seen the two jacks are wired in parallel.