[Asterisk-Users] some EICON Diva 4BRI questions

[Armin Schindler]

On Thu, 27 Apr 2006, Klaus Darilion wrote:
> Armin Schindler wrote:
> > On Wed, 26 Apr 2006, Klaus Darilion wrote:
> > > On Sun, April 23, 2006 16:30, Armin Schindler said:
> > > > On Sat, 22 Apr 2006, Klaus Darilion wrote:
> > > > > But I'm still confused. Usually, if a line needs termination,
> > > > > the
> > > > > termination is needed on both ends. Thus, if there is no line
> > > > > termination
> > > > > inside the DIVA card, we would termination in TE mode too.
> > > > Sorry, I don't know why this is different to 'normal' ISDN line.
> > > > Maybe
> > > > the difference is about the distance. A normal ISDN line may be
> > > > more than
> > > > a
> > > > few meters, but in NT-mode I have my PBX/Equipment connected to
> > > > the card
> > > > with a one meter cross-cable.
> > > > 
> > > > I will try to find out more about this.
> > > Hi Armin!
> > > 
> > > Could you find out something?
> > 
> > Yes, I asked Eicon. The cards don't have internal termination. The ports
> > are
> > layed out for TE mode, so depending on your ISDN bus topology, you need a
> > termination.
> > And you are right, when in NT-mode both sides needs termination.... just
> > normal ISDN bus topology.
> 
> This still confuses me. In P2P mode, there is always one device in NT mode,
> and one device in TE mode. Usually termination is needed on both sides of the
> cable.

Yes, but when you have a normal ISDN line (NT comes from Telco), then you 
have the termination in the NTBA (configurable with switches).
 
> If the EICON DIVA does not have termination resistors inside (IMO a real
> weakness, all the cheaper cards do have them and you can enable them with
> jumpers), I would think that we need external resistors in both cases,
> regardless if EICON DIVA is in NT or TE mode.

That is not a weakness! The termination depends on your bus topology, so you 
should add the termination in the box at the wall when needed.
Maybe some cards do have own termination on board, but this then need to be 
optional. I don't know any ISDN phone, which has own termination.
 
> > Since I have only one termination in the middle of my cross cable, which
> > works fine, I assume that the termination is not really necessary on both
> > sides when having just a one meter cable.
> 
> btw: do you know where I can by this cables (I do not like soldering)? Does
> EICON offer this cables (for fixing their design bug)?

I'm not aware of such a cable to buy. Normaly, when you create a NT-side the 
connection is not made with just one cable (like I did because both device 
are just 10cm away from each other). In most cases you have an ISDN bus 
cabled in the rooms where the necessary changes (other termination, crossed) 
can be done in the boxes. I don't see any design bug here.

Armin