Peter Svensson wrote:
On Tue, 22 Mar 2005, McQuiggan, Mark xt46480 wrote:
I am using a SIP softphone (X-lite, SIPPS or Firefly) connected to an Asterisk v 1.0.3 PBX. The PBX is also connected via a ISDN-PRI crossover cable to a Avaya Definity Generic 3 PBX via a TE405P card. All outside of the office calls go through the Definity. Here's the issue:
Calls to internal SIP extensions, Definity extensions, other offices within our private network (through the Definity), and cell phones are great. When I call outside of the office to POTS lines (like my home), there is a most noticeable echo of my voice. The party on the line hears no echo. Any efforts on the configuring the SIP softphones, and within zapata.conf, have been for naught.
Is this problem common for ISDN-PRI connections?
It is a problem you will see when calling an analogue subscriber over a link with a long latency (such as VoIP). The echo will most probably be generated by a 2- to 4-wire hybrid at the far end. In a pure amalogue/tdm path you would perceive the reflected energy as a plesent sidetone. As soon as the latency increases to 50-100ms the refelcted energy will be perceived as an echo instead.
The options available to you are to live with the echo of your own voice or to insert an echo canceller at the pstn interface. Asterisk includes an echo canceller that may or may not be good enough. It seems to like some pstn interfaces and not others. If the Asterisk echo canceller is not enough you may consider an expensive inline echo canceller.
The definity has echo cancellation. Try turning that on.
-SteveK
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