[asterisk-users] Dropouts and echo

[Tom Lanyon]

Hi all,

We have recently implemented an Asterisk system using Trixbox  
(asterisk v1.4.4 at the moment, yet to move to 1.4.9) but are getting  
pressure to switch back to our old key system unless we fix two major  
issues. So please help me avoid switching back!

An overview:  We have about 12 Linksys SPA941 SIP phones connected on  
a private switched network to our asterisk box which is a highly- 
specced HP xeon server. This in turn connects to an Epygi gateway  
( http://www.epygi.com/quadro-gateway/70/#isdn ), bringing in 4 ISDN  
BRI lines as a SIP trunk.

The issues:
	Dropouts - by far the most serious issue we've encountered. On most  
calls (normally anything longer than 1 or 2 minutes), suddenly one  
end of the call will go silent and not be able to hear the other  
person. After a few seconds of "I can't hear you!" the audio returns  
and continues normally. This seems to happen whether it's an internal  
call between SIP devices or whether it involves a call via our ISDN  
gateway. At first we believed this was just when we had our phones on  
'speakerphone' and that it was an issue with the physical SIP phone  
itself, but we're now also finding 'dropouts' just using the phone  
handset aswell.

	Echos - on a majority of calls we can hear an echo of our own voice,  
a few milliseconds later (enough to be very annoying). From all I've  
read regarding echo in a VoIP system, I understood that echo was  
normally introduced by a non-voip device in the system (in our case  
the external ISDN lines). However, we are having echo produced on a  
call between two internal staff members between their respective SIP  
phones.

Can anyone advise what could cause either of these and what we can do  
to try and investigate them?

Thanks,
Tom