[asterisk-users] OT - Incoming fax cuts ADSL line

[James Sharp]

On 5/16/2012 12:07 PM, Tim Nelson wrote:
> ----- Original Message -----
>> Hi,
>>
>> I'm facing a strange situation.
>> Though it's not directly related to Asterisk, I do think it is
>> interesting to this mailing list.
>>
>>
>> The setup is a single line which is split between an ADSL
>> modem/routeur and a fax machine (Asterisk was removed from the
>> equation).
>>
>> Any time the fax machine rings (incoming fax), the ADSL service is
>> troubled to the VPN users are disconnected.
>> It can be reproduced at will.
>>
>> I've changed the ADSL filter twice (a different unit, then a
>> different
>> model) without any visible change.
>> What could explain this ?
>>
>
> I've experienced this quite a few times, and after working with a local telco, it has become policy to not place ADSL on lines where fax is going to be used. I'm unsure of the exact technical reasons behind this other than 'the fax signals/frequencies interfere with the ADSL signalling/frequencies used on the circuit'. It sounds like you might want to separate your fax/ADSL lines.
>
> --Tim

You might also be able to limit the Fax machines maximum transmission 
rate so the modem's transmission spectrum doesn't inch up into where the 
ADSL service is.