[Asterisk-Users] two isdn cards

[Alex Vishnev]

Mike,

The cable needs to be a cross-over cable when connecting directly between 2
T1s, bypassing PSTN. One side of isdn has to be configured as TE and the
other as NT. Only 4 wires are needed (not full 8 wires) to build a T1
cross-over. If you are connecting the systems thru pstn, you need regular T1
cable. Also, please remember to configure timing/clocking on both systems.
If you are connected to pstn, then you will need to configure slave clocking
on your side. If you are connecting 2 systems without pstn, then one must
generate clock and another slave clock. Without proper t1 clocking you will
see frame slips and errors on t1 line. ISDN is very sensitive to clocking,
while regular RBS t1 can function with with frame slips, except you may hear
pops/clicks or missed in your audio stream. 

HTH

Alex

-----Original Message-----
From: asterisk-users-bounces at lists.digium.com
[mailto:asterisk-users-bounces at lists.digium.com] On Behalf Of Stankiewicz
Michael
Sent: Monday, May 23, 2005 11:49 AM
To: Asterisk Users Mailing List - Non-Commercial Discussion
Subject: Re: [Asterisk-Users] two isdn cards

thanks a lot,
i've googled around hunting for an answer to my biggest doubt: the
cross-cable.
i understand that it looks like an cat-5 cross-cable and how it has to
be done, but ... why 8 wires ? 
i found this image: http://www.gcom.com/home/support/t1crossover.html
and that one:
http://www.voip-info.org/wiki-crossover+T1+cable?page=crossover%20T1%20cable
&comments_threshold=0&comments_offset=0&comments_sort_mode=commentDate_desc
...
so: the cable that goes from the isdn NT to asterisk should be an 8
wires isdn-cross-cable ?

thanks for those newbye delightenments :)
ciao
mike


On Mon, 2005-05-23 at 16:50, Emanuele Pucciarelli wrote:
> Stankiewicz Michael wrote:
> 
> > i followed this how-to:
> >
http://www.voip-info.org/tiki-index.php?page=Asterisk%20zaphfc%20install26
> > having in response no sign of life.
> 
> If the module doesn't even get installed, or the kernel does not report
> any card as recognized, you could tweak the initialization routines to
> add PCI IDs for your own cards, and hope they work correctly.  If the
> cards are recognized, there should be nothing to worry about: either
> they work with zaphfc or they don't, modulo interrupt troubles.
> 
> > the software side is pretty straightforward but i have many doubts on
> > the hardware deployment:
> > 1- the idsn cable going from asterisk to the NT sould be a cross cable ?
> 
> Yes.  But not an Ethernet cross-cable, an ISDN cross-cable; there's a
> pointer on the wiki to a page on isdn.jolly.de explaning how the cable
> should be made, and suggestions about how to take advantage of a disused
> NT.  I reckon that telephony folks call it an "ISDN TX/RX" cable.
> 
> > 2- it should have 100 ohm resistors (if yes, where can i find the
> > schemes )?
> 
> Yes, the bus should be terminated (so the resistors don't have to be on
> the cable itself).  A full description of the bus is in the ETSI
> standard for ISDN layer 1 (www.etsi.org).

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