Summary: How to make sure your microfilters are correctly fitted.
  1. Why do I need to use microfilters?
  2. What does a microfilter look like?
  3. How do I connect a microfilter?
  4. How many microfilters do I need and where should I connect them?
  5. I'm having problems and need to check my microfilters, what should I do?

1. Why do I need to use microfilters?

Microfilters (also known as 'ADSL filters' or just 'filters') stop broadband and voice signals interfering with each other. Without microfilters, you'll have problems with your connection and speed. You may also hear high-pitched noises when using your telephone line.

Please note: You don't need microfilters if you're a Plusnet Fibre customer or you have an ADSL Faceplate (what's this?).

What's an ADSL Faceplate?

An ADSL faceplate has built in microfilters two sockets (One for DSL and one for Telephone devices). If you have one of these installed in your property, you will not need to use standard microfilters in other sockets as your line is already filtered.

They look like this:

An ADSL Faceplate with built in microfilter.
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2. What does a microfilter look like?

They look like a telephone adapter/line splitter (a device that lets you connect two telephones to one line).

Each microfilter has two sockets:

  • One is to connect to your router (usually labelled ADSL or DSL)
  • The other one is to connect a telephone handset or other device (e.g. a Fax machine or Digital TV box)
A typical microfilter
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3. How do I connect a microfilter?

It's easy, just follow the steps below:

Step 1

Remove the existing telephone cable from your wall socket.

Remove the existing telephone cable from your wall socket.
Step 2 Plug the microfilter into the empty socket. Plug the microfilter into the empty socket.
Step 3

Plug the phone cable into the microfilter's phone socket.

Plug the phone cable into the microfilter’s phone socket.
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4. How many microfilters do I need and where should I connect them?

You need to connect a microfilter to each phone socket used in your property, as shown in the example above.

Phone sockets can used by phones, alarm systems, fax machines and digital TV boxes, make sure you don't miss anything out (don't forget to check all floors of your property). Most router packs include two microfilter. If you need more, you can get them from most electrical stores and supermarkets.

Follow these rules to avoid problems with your microfilter setup

  • If your router is plugged into an extension cable, only use a microfilter on one end - not both
  • Avoid 'double filtering' - don't connect one microfilter to another
  • You can connect two or more telephone devices to one microfilter if you have a splitter
  • Don't have enough microfilters? - leave something unplugged until you can get some more
  • Not using one of your phone sockets? - no need to connect a microfilter
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5. I'm having problems and need to check my microfilters, what should I do?

Unplug everything from your telephone line and connect your router directly to your master telephone socket (it should be the one closest to where the telephone line enters your property. Please see our Master socket guide if you need help).

A router connected directly to the master telephone socket
  • If this fixes the problem, something you've unplugged was the cause. Find it by reconnecting your devices and checking for problems after each one. You'll probably find that something isn't connected to a microfilter, or that one of your microfilters is faulty
  • If this doesn't fix the problem, try another microfilter. If there's still a problem you should report it to our Support Team
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This page last updated 18th November 2011

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