Weird phone/modem interference

grumpycrab

Looking at a friend's noisy phone/intermittent broadband (ADSL upto 17Mbps)...
Phone is fine with ADSL router/modem unplugged; plug modem in and after a couple of mins get modem/fax noise on the phone line; unplug modem and within 10 seconds the phone line goes quiet; ZEN said try a different router - same problem.

Also swapped RJ11 and ADSL filter.

My theory - something is trying to send a fax (on a loop) to friends number - but it only causes phone noise when his ADSL modem is plugged in. ZEN say line fault. Awaiting BT...

agrinnall

Does your friend actually receive faxes on that number? I can't remember the last time I sent or received a fax but perhaps it is a business that needs a piece of paper rather than an email.

mgfvvc

grumpycrab wrote: »

Looking at a friend's noisy phone/intermittent broadband (ADSL upto 17Mbps)...
Phone is fine with ADSL router/modem unplugged; plug modem in and after a couple of mins get modem/fax noise on the phone line; unplug modem and within 10 seconds the phone line goes quiet; ZEN said try a different router - same problem.

Also swapped RJ11 and ADSL filter.

My theory - something is trying to send a fax (on a loop) to friends number - but it only causes phone noise when his ADSL modem is plugged in. ZEN say line fault. Awaiting BT...

I think Zen are spot on. I had a similar problem. I took it back to the master socket and an ADSL microfilter. I ran quiet line tests, starting with the router turned off and you could hear the noise start as soon as the ADSL light came up on the router.

Openreach changed a lot of wiring, etc., but it seems to have been resolved when they fixed a connection at the telegraph pole.

I can't see where fax would come into it. The phone would ring for an incoming fax and there would be no fax noise until the phone was picked up.

grumpycrab

mgfvvc wrote: »

I think Zen are spot on. ...
I can't see where fax would come into it. The phone would ring for an incoming fax and there would be no fax noise until the phone was picked up.

Thanks. Ok, not fax - dial-up modem connection noise. And then a load hiss (like data). There IS a fax machine connected but not used for about 3 years (and I tested at the test socket with fax machine removed). Has to be a red-herring.

System

grumpycrab wrote: »

Has to be a red-herring.

Red herrings are renowned for causing interference on ADSL lines. Try a nice bit of hake instead :rotfl:

kwikbreaks

That fax machine might be worth a few bob to a museum.