[Asterisk-Users] ISDN Hardware

[Peter Svensson]

On Fri, 28 Jan 2005, Jeff Lists wrote:

> I have a test install set up as follows
> 
> Grandstream 102 ---- Asterisk ---- X100P ---- Adtran Express 3000 ---
> ISDN line to PSTN
> 
> Most things I want to do work fine except I do have some intermittent
> problems with an echo.  I am assuming that this is created in the link
> between the X100P and the Adtran terminal adaptor.

Probably, but it could also be far end echo. These are hard to get rid of.

> I am not sure of the proper terms but on the PSTN side of the Adtran
> there is one pair of wires which carry two channels.  On the interior
> side of the Adtran there are two pairs of wires which each carry one
> channel (is this a BRI channel??).

A BRI has two voice (or generic data) channels (two B channels) and one 
signalling channel (the D channel).

> In the final install I will be replacing the X100P with some type of
> ISDN card.  I currently have three ISDN pairs which create six lines. 
> I would like to get enough hardware to be able to add one more pair of
> lines soon.
> 
> My question is what type of ISDN card do I need?

ISDN BRIs are delivered differently in different parts of the world. We 
need more information to help you.

> Will this replace the Adtran or plug into it?
> Since this is all digital is it a safe assumption that my echo
> problems will be gone?

You will not *cause* any echo, especially not to the far en customer. The 
far en customer may still cause an echo which you will hear. The VoIP step 
to the phone may bring the echo from nice sounding sidetone to nasrt echo. 
The built in echo canceller may help if this is a problem.

Peter