Extension on BT Master Socket 5C - Connecting BT Router?


Standard Member

Just had BT to come out to identify a broadband fault, and they replaced my old BT master socket with a new dual-plug one "5c" - with a built-in microfilter. Fancy!

My router is usually plugged in in another room, via a normal telephone extension cable. However as I have a new master socket face-plate, this does not work. I cant plug the router cable directly into the extension, the cables are different. The engineer did connect the extension cable to the new master socket face-plate, and it works with a phone no problem.

BT now want to charge me £150 to put an old face-plate back on, but is there another way?

Is there a converter I can use to convert the router's cable format into the one on the telephone extension? (with no microfilter) or another solution perhaps?

I have the 600MBPS homeplugs already, but my house has two different wiring systems so they do not work well between the two parts of my house.

Regards in advance

Adrian Williams


Last edited:


Distinguished Member
You can rewire the extension at the master socket to return it to unfiltered if the master socket has A & B connectors.



Well-known Member
You are sacrificing performance by having your router plugged into an extension. Extensions them selves can also cause a reduction in sync speeds sometimes. I’d highly recommend that you reconsider where you have your router located. If losing a few Mbps isn’t an issue for you then of course that’s fine.
You can buy a standard 5C MS and just swap the faceplate, which would allow you to plug a micro filter and router into your extension socket again.
NTE5C OpenReach Telephone Master Socket + M3.5 Machine screws included.


Distinguished Member
It sounds like the extension cable has been attached after the filter.
You can rewire the extension at the master socket to return it to unfiltered if the master socket has A & B connectors.

Going by the pictures he appears to be talking about an extension cable plugged into the socket on the front of the faceplate rather than a normal phone socket extension wired into the back.

As it's plugged into the internet side it shouldn't be filtering the VDSL signals and we know the extension cable is capable of carrying the signals as it was working before.

Have you tried plugging the router into the master socket directly to make sure that works? If it's faulty then the extension is irrelevent.


Well-known Member
I fit these sockets on a daily basis. Pre filtered socket is also filtering the extension socket so if you try and plug in a micro filter you are double filtering. If you don’t want to simply swap the face plate like I suggested above you could try replacing your adsl cable with one that has an RJ11 on one end a phone jack on the other, plugging the phone jack straight into the socket. I’ve never tried it but in theory it should work.

Similar threads

The latest video from AVForums

Podcast: Home AV, TV, Tech News & Reviews, Plus The Best of July 2020
Top Bottom