Sudla,

White noise is a random noise signal that has the same sound energy level at all frequencies or stated in another way, sounds containing every audible frequency at approximately the same intensity.

The following is a typical example of a Microfilter as used in the UK

This ADSL micro filter allows you to share broadband and analogue telephone equipment on one socket.

To ensure the quality of both the telephony and the ADSL, it is important that every piece of telephony equipment must be filtered including telephones, fax machines and even simple tone callers. This doesn't mean that every piece of equipment has to have a filter, only that every telephone socket that has telephony equipment attached to it should have a micro filter fitted first.

Hello again!

The white noise stops as soon as I unplug the router and I have microfilters on both lines, so I am well and truly stumped!

When you say "as soon as I unplug the router" do you mean unpluging the power to the router and leaving the phone line connected ?

OR do you mean unplugging the router phone line and leaving the router power connected or unplugging both ?

Andy T.