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… install an New Style NTE5c BT / OpenReach etc Telephone Master Socket – replacing NTE5a

My guide to installing a New Style BT OpenReach NTE5c Telephone Master Socket … New Version.

A circuit diagram of the BT OpenReach NTE5c Telephone Master Socket.

C1 = 1.8μF Capacitor
R1 = 470KΩ Out of service resistor
R2 = Bell Wire Resistor/Choke (Colouring says ?Ω – meter reads 77Ω)

Inside the NTE5c Telephone Master Socket 5c. Components from left to right. R1, service resistor, R2, bell wire resistor, C1, ring capacitor.

There are 3 components in the NTE5c master sockets now – the Ring Capacitor, Test Resistor and a bell wire resistor/choke. These components are all on the back plate of the NTE5c – as is the extension wiring – but the extension wiring remains disconnected from the line until the lower half faceplate is plugged in. Master sockets have not contained the Surge Protector since around 2012 as these can cause issues with Fibre BroadBand.

When fitting any new socket:-

  • Never strip any wires going into the IDC connectors.
  • Always connect to the next available bit of fresh, unused wire.
  • The wires on A, B, 2 (3*) and 5 on your current socket will be going to the same positions on the NTE5c.

* 3 is used to carry the ring signal, but is known to cause issues with broadband. I personally never use as most modern phones don’t need this – if your telephone on the extension socket requires a ring capacitor, use a decent microfilter that contains the ring capacitor.

Incoming cable … Always connect to the next available bit of fresh, unused wire. Cut used/damaged cable off.

To connect the incoming line place the clean un-stripped cables in the A and B connectors as shown, making sure the cables pass through both holes and go right to the back of the cam-lock IDC connector. These will be the same 2 cables you removed from A and B on your current socket.

Making sure the wires stay in place, now close the cam-lock IDC fully. If you need to open this cam-lock for any reason you need to cut off the used bit of cable then follow the above again. Never re-use the same section of wire in any IDC connector.

On the newer MK2 version of the NTE5c, they now have clear cam-locks so you can see that the cables are correctly placed.

If you have no extension wiring to install, screw this unit to your backbox then test using the test socket, see picture below, or just clip the lower half faceplate and use as normal.

NTE5c Telephone Master Socket – test socket. Note; your extension wiring will not be connected when the lower-half face-plate is removed.

NTE5c Telephone Master Socket – finished.

Note: Even though the extension wiring is now in the main body of the NTE5c, it will remain unconnected from the phone line until the lower-half face-plate is installed.

To install the extensions cables, again used clean un-stripped wires in the 2 and 5 connectors as shown, making sure the cables pass through both holes and go right to the back of the cam-lock IDC connector. These will be the same 2 cables you removed from 2 and 5 on your current socket. Again, on the newer MK2 version of the NTE5c, they now have clear cam-locks on the extension IDC’s so you can see that the cables are correctly placed.

Important. If you have 2 extensions coming from your current master socket, note these will both need to be placed in the cam locks at the same time and on top of each other, make sure they’re not twisted as this will damage the IDC.

Clear on NTE5c MK2.

If your extension wiring comes out the front of the socket, it just comes straight down, there is a cut out in the lower half faceplate to accommodate this.

If your extension wiring comes in through your backbox, route the cable as shown in the 2 pictures below – running the cable along the bottom of the socket, then out the right-hand side of the hole.

Rear view of extension wiring.

NTE5C fitted, finished.

Below is a mock up of NTE5c and VDSL MK4 filter used to – this is the best option if you wish to have the broadband router anywhere except at the master socket.

Using NTE5c + VLDS MK4 to move broadband router away from master socket.

Standard incoming BT line (drop wire)


Standard incoming BT line (drop wire) – Close up. The Steel Tension Cables can be other colours, but all 3 are always the same colour.


The NTE5’s come with 2 choices of mounting screw. If using a plastic backbox without any metal in the mounting holes, use the self taping screws, otherwise use the machine screw – the machine screws are also for use on the metal back box sunk into wall.

Wiring extension sockets on the faceplate:-

2 = Blue with white rings
3 = Orange with white rings – Don’t connect for best internet speeds.
4 = Not on new sockets, or
5 = White with blue ring

If your telephone does require a ring capacitor, use a decent microfilter that contains the ring capacitor.

Like these.

Can be bought on Amazon for about £8. http://amzn.to/2pt2CZn

Or eBay. ebay.co.uk

{ 12 comments… add one }
  • Steve Samain September 27, 2017, 15:12

    Is this the same way to connect the new MK4 master box with the 2 sockets fitted 1 for telephone the other for adsl

    • Dave Fry September 27, 2017, 15:36

      Hi, yes, they come as one unit. You don’t get the little half faceplate as shown above, you get the VDSL MK4, this clips on the front. Be careful with any extension wiring as there’s not a lot of room behind the MK4’s.

  • John Whaley October 3, 2017, 15:04

    Great instructions, but BT tell me that they will charge me £130 plus VAT if |I have changed the master socket which I want to do to check if any faults are in the house or prior to the socket.

  • Pete October 18, 2017, 08:14

    Hi Dave,

    Great tutorial. Just have two question regarding the data extension. In your last image you show the MK4 with the red IDC camlock on the filter plate. I believe these are labelled A and B (cannot tell from your picture which is which, (orange (upper hole) white/orange (lower hole)). My question is two fold, what pins on the rj11 plate/socket should these two be connect (I believe it is pins 2 and 3 (middle two) and secondly does it matter which way round they go. At the moment I believe they should be A->2 and b->3.



  • John October 19, 2017, 13:58

    Hi. I have some serious noise problems and I am in the process of renewing the VERY old BT wiring scheme. The original Master socket is an LJ3/1A I have just purchased a MK5 master skt from you and your data sheet doesn’t help here. In the last couple of years an Open Reach engineer installed a DSL service and installed a MK3 Master Socket. I have just upgraded to VDSL and phone wont work and Data service has many drop-outs. The BT incoming cable has 4 pairs; solid blue, Orange Green and Brown and has 4 white. Looks like BT have used Blue and Orange as incoming line and Green and Brown for extensions. Is this correct please.

  • Eoin Selfridge October 31, 2017, 21:23

    Hi I have master socket with internet on top and phone on the bottom, internet is working fine, phonesocket gone dead have use test socket when I take cover off all I get is a hiss have try a few phones any ideas

    Eoin selfridge

  • tony whoami November 7, 2017, 12:23

    so if I swop the lower part of my nte5c master socket and run a cable from the a&b (on the mk4 vsdl face plate) and the 2 & 5 (on the nte5c) to where I need the socket to be it should work?
    if that’s right can you recommend a face plate that has phone and router ports?

  • Neil March 17, 2018, 21:42

    Does it matter which way round the incoming orange white wires are connected. In my old socket orange goes to A and white to B

    • Dave Fry March 19, 2018, 12:32

      I’ve always connect White to A and Orange to B. But polarity isn’t an issue, except on some old old fax machines and alarm systems.
      Hope this helps.

  • Andy December 5, 2018, 19:12

    Hi Dave,

    I am moving into a flat and the master socket is stuffed in a cupboard with no real plug / access for a router.

    All of the rooms (two bedrooms and lounge) have ADSL phone line sockets in. Is there an easy way to flip the VDSL to the desired extension port?

    I know a article on vmadmin shows simular things

  • Emma Jenkins December 23, 2018, 09:21

    Hi Dave

    The wires I have are:
    Green -white & white green
    Organe white & white orange
    Blue white & white blue

    I have the mk4 open reach face plate

    Kind regards

  • Steven Cartwright January 26, 2019, 17:23


    If you have a plastic box what size self tapping screws would you need to attach the nte5c to the back box? Mine only came with machine screws.



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