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

[Chad Wallace]

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.


-- 

C. Chad Wallace, B.Sc.
The Lodging Company
http://www.lodgingcompany.com/
OpenPGP Public Key ID: 0x262208A0