[INFO NEEDED] Asterisk & ISDN & Echo Cancellation

Hi guys, I am working on an Asterisk based call centre and I am dealing with the following dilemma: the Asterisk PBX will be connected to an ISDN line (via E1 Sangoma card), but I don’t know whether do I need an E1 card with the Echo Cancellation features or not? What are the chances of echo appearing in my configuration?

Have a look here:

voip-info.org/wiki/view/Aste … ncellation

[quote=“MuppetMaster”]Have a look here:

voip-info.org/wiki/view/Aste … ncellation[/quote]

Thanks! :smile: I went through these documents, but I am still not quite sure whether do I need an E1 card with echo cancellation or not.

If I understood everything correctly, the source of the echo can already be the caller’s telephone. In that case it doesn’t really matter to what & how the Asterisk is connected to the rest of the world. In theory I would need to handle echo in any case. Or am I wrong?

I have a small Asterisk install that started with an AVM!Fritz passive BRI card (no cancellation). After much trouble trying to get two of those cards in a single machine, I swapped it for an Eicon Diva V-4BRI active card with echo cancellation. The difference is noticable. I had intermittant echo problems with the AVM card and have yet to have any significant echo problems with the Eicon.

Your mileage may vary, of course. :smile:

You can still get echo when you are completely digital end-to-end.

I have a set up where I have SIP phones connected to an Asterisk at one site, which then communicates with an Asterisk at another site which has the E1 card connected to a PRI for outbound PSTN calls.

I have to apply echo cancellation in order to remove echo caused by the latency between the user’s SIP phone and the Asterisk with the E1 card (this can vary from 30-60ms).