[asterisk-users] Static noise on bridged calls to PSTN, although the trunk line is clean on its own

Sebastian Arcus shop at open-t.co.uk
Wed Sep 12 17:33:16 CDT 2012

On 10/08/12 18:38, Chad Wallace wrote:
> On Tue, 31 Jul 2012 09:44:26 +0100
> Sebastian Arcus<shop at open-t.co.uk>  wrote:
>> I have two setups with SIP hardware phones as extensions and POTS
>> lines as trunks. Internal SIP to SIP calls are crystal clear, but all
>> calls bridged to POTS have a significant amount of static noise. The
>> problem is that if I plug a POTS phone directly into the line, there
>> is almost no static noise - the line is clean. It's like Asterisk (or
>> the hardware) amplifies the static noise. What I've tried so far:
>> 1. Connect Asterisk with a short cable directly into the master phone
>> socket, where it enters the building.
>> 2. One of the lines carries ADSL - so I double filtered it.
>> 3. Tried three different phone sets (one Grandstream, two Cisco
>> models).
>> 4. Tried an OpenVox A400P PCI card and a Sangoma U100 USB
>> adapter as analogue-to-digital interfaces.
> Have you run fxotune?  I remember doing that when we had analog
> lines.  You'd have to look up how--maybe just in the fxotune man page.
Thanks for replying Chad - and sorry for the delay in my reply. I should 
have mentioned that I ran fxotune and made no difference. I also checked 
the interrupts, and even changed motherboard, and tried a USB analog 
adapter (Sangoma U100) instead of the current OpenVox PCI adapter. None 
solved the problem.

I have given in and asked the client to order ISDN lines I'm afraid.


Linux vehicle CCTV - www.open-t.co.uk/iroko

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