Why do I need ADSL filters (microfilters) and where do they go?

A microfilter is a device that allows broadband to work at the same time as your phone service. Without microfilters you may get problems with your BT Broadband or hear noise on your phone line. Normally, you'll need a microfilter for every phone socket in your home where you've got some kind of telephony or broadband equipment plugged in.

A microfilter is a device that allows broadband to work at the same time as your phone service. Without microfilters you may get problems with your BT Broadband or hear noise on your phone line.

If your master socket has one socket:

Master socket with one socket

You must use a microfilter for every phone socket in your home with any phone or broadband equipment plugged in (including your Hub, phones, answer machines, digital TV boxes, and alarm systems).

If you need to order more microfilters from BT, go to www.bt.com/shop >

Using a Hub with a microfilter

If your master socket has two sockets, like this:

Master socket with two sockets

You must always plug your Hub into the broadband connection on your master socket. If you plug it into a phone socket or extension, it just won't work.

You don't need microfilters - not for your Hub or any other devices connected to phone sockets or extensions.

Master socket with two sockets

Set up rules and scenarios

  • The microfilter must be the first thing connected to the master socket, followed by any other equipment
  • Avoid using extension cables for your Hub as they may cause problems with your connection. If you must use one, then use a new, high quality broadband ADSL extension cable
  • To connect more than one device to your phone line, you'll need a splitter. The splitter must connect to the phone part of the microfilter
  • If you're trying to connect a BT TV box, this connects via Ethernet to your BT Hub.

    Find out more about setting up BT TV >

  • Some other TV services need a phone line, in which case the TV box must connect to the phone part of your microfilter. Please refer to your user guide or TV service provider for help

Video: How to fit a microfilter

Watch our video to see how to fit a microfilter to your telephone line.

Setting up microfilters - some common scenarios

Scenario 1: Simple set-up when your phone and Hub can both be near your master phone socket.

Simple microfilter set-up

Scenario 2: Set-up where the phone is connected near the master socket and the Hub is located further away using an ADSL extension cable. Remember - using extension cables can affect your connection.

Microfilter set-up with extension sockets

Scenario 3: Set-up where the phone and the Hub are located far away from the master socket.

Microfilter set-up with Hub on extension lead

Scenario 4: Scenario showing how to connect a third party set top box that needs a phone connection. The TV box connects to the phone part of the microfilter via a splitter. The phone connects to the other port of the splitter.

Microfilter set-up with phone on extension lead

 

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