Hello, I have a crossover PRI(Asterisk server to PBX) and a regular telco PRI T1 line and currently have echocancel=yes and echocancelwhenbridged=yes on those spans in zapata.conf. I was discussing CPU load with another Asterisk user and he mentioned that PRIs don't need echo cancelation and that turning it off will reduced CPU load on the server. I checked many sample configs and the archives and noticed that half of the people have echocancel on for PRIs and half do not. I checked the Digium site and indeed in the FAQ they say: "There should also be no echo on PRI connections". Does it really matter that much in terms of CPU usage and will it hurt at all if I turn it off for the crossover PBX connection or the telco PRI that I have? Thanks, MATT---
mattf skrev:> I checked many sample configs and the archives and noticed that half > of the people have echocancel on for PRIs and half do not. I checked > the Digium site and indeed in the FAQ they say: "There should also be > no echo on PRI connections".If you need echo cancelling on the PBX PRI depends on the phones used on that PBX. If they are all digital and they do not introduce any echo you will not need any echo cancelling. On the T1 side you will probably need echo cancelling since there might be an analog phone in the other end. If you only use PRI in and out on the same asterisk server the delays may be so short on a bridged call that the echo would not be noticable even if it is there. That is the way ordinary pstn calls work - there is usually echo cancellation only on cellular calls or long distance calls. -- Regards, Tobias J?nsson, Lund SE
Tobias J?nsson wrote:> If you need echo cancelling on the PBX PRI depends on the phones used on > that PBX. If they are all digital and they do not introduce any echo you > will not need any echo cancelling.The outside phone will still (usually) be analog and cause echo. So unless you are only calling other VoIP or cell phones you still need echo canceling when using PRI.
Eric Wieling wrote:> Tobias J?nsson wrote: > >> If you need echo cancelling on the PBX PRI depends on the phones used on >> that PBX. If they are all digital and they do not introduce any echo you >> will not need any echo cancelling. > > The outside phone will still (usually) be analog and cause echo. So > unless you are only calling other VoIP or cell phones you still need > echo canceling when using PRI.Yes, that is exactly what I wrote??:> On the T1 side you will probably need echo cancelling since there > might be an analog phone in the other end.-- Best Regards, Tobias J?nsson, Lund SE
I get sideband (interpreted by the enduser as echo) when calling a POTS line through our PRI on Snom's or X-Ten. Our crappy BudgeTones actually sound the best. Everyone is exactly right here, that it really depends how the call is terminated on the other side. Calling from a Snom terminating to a PCS cell, for example, is crystal, no sideband at all. I'm assuming that the PCS carrier is doing their own echo cancel / sideband reduction. I dealt with my issues by simply cranking down the gain on the PRI (dramatically, I think I am at -15 Tx) . Every PRI from every carrier has different gain values; on my PRI, the carrier has it cranked to the max. Fiddling with gain values was, at least for me, the most effective way of eliminating the issue.
> I have a crossover PRI(Asterisk server to PBX) and a regular telco PRI T1 > line and currently have echocancel=yes and echocancelwhenbridged=yes on > those spans in zapata.conf. I was discussing CPU load with another Asterisk > user and he mentioned that PRIs don't need echo cancelation and that turning > it off will reduced CPU load on the server. I checked many sample configs > and the archives and noticed that half of the people have echocancel on for > PRIs and half do not. I checked the Digium site and indeed in the FAQ they > say: "There should also be no echo on PRI connections". > > Does it really matter that much in terms of CPU usage and will it hurt at > all if I turn it off for the crossover PBX connection or the telco PRI that > I have?I recall working with someone that had echo on their pri, and turning it one resolved his issue. Play with it to see what impact it has on your case.