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Master or secondary telephone socket

Updated: October 2026

Two BG plates, 8BTM and 8BTS, or an NTE faceplate beside a small jack, can share the words telephone socket and still be different jobs. The master or secondary telephone socket choice is one fork. The master is where the line enters and feeds the other sockets. Every later point is a secondary. A second master is not a spare, and a secondary will not stand in as the only socket on the lead-in. The eight listings are on the [telephone socket comparison](/hub/sockets-and-extension-leads/telephone-socket). Box, terminals, and finish come next, on the [telephone socket buying guide](/hub/sockets-and-extension-leads/telephone-socket/sub/telephone-socket-buying-guide).

Two BG plates, 8BTM and 8BTS, or an NTE faceplate beside a small jack, can share the words telephone socket and still be different jobs. The master or secondary telephone socket choice is one fork.

Our top picks

1STec NTE5c MK2 faceplate, tool-less IDC

Best overall

1STec NTE5c MK2 faceplate, tool-less IDC
9.2/10about £9.95
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British General BG white secondary, screw

Best value

British General BG white secondary, screw
8.8/10about £3.89
View offer
British General BG white master, screw

Alternative

British General BG white master, screw
7.4/10about £5.99
View offer
On this page
  1. 1.The one fork
  2. 2.Why a second master is the wrong spare
  3. 3.NTE faceplate or a single-gang master
  4. 4.Which kept listing is which

The one fork

Put the master at the entry. The line lands there, and the cables to other rooms leave from it. Put a secondary in the bedroom or the hall, in parallel. The historical rule here is one master on the exchange cable. An archived OFTEL wiring code, kept by Sam Hallas, says a master is not approved as an extension and can upset the system. That document is a historical code, not a 2026 shopping statute. It is still why two similar plates are not interchangeable. thinkbroadband treats an 85 mm plate with a horizontal split as the NTE-style master, and a non-split 68 mm plate as an old socket or an extension. The test socket lives behind the lower half of the split plate. If a remote point has only two wires and the bells are the problem, that is terminal 3 on how to fit a telephone socket, not a cue to order a second master. Full fibre is a separate stop on telephone socket on full fibre.

Why a second master is the wrong spare

A master holds the components that present one extension circuit after the line. A second master puts those components where an extension should be. Trade notes describe that as a cheat when the bell wire is missing, and a phone that rings continuously when terminals 2 and 5 are swapped. Restore terminal 3, or accept extensions that do not ring. Do not add another master. Two masters also confuse the test. BT’s test socket is on the real master. Openreach keeps the NTE as its property, and a wasted fault visit can be charged. The limit is the same: one master. Model 8BTM/1 (B004TRRV48) is the master at £5.99. Model 8BTS/1 (B004TRRVA2) is the secondary at £3.89. Both are 86 mm screw plates with a BS 6312-2 claim. The cheaper one is not a bargain master.
1STec NTE5c MK2 faceplate, tool-less IDC

Testsieger

1STec NTE5c MK2 faceplate, tool-less IDC
9.2/10about £9.95
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NTE faceplate or a single-gang master

An Openreach NTE5 is about 85 mm with a split front. You may replace the customer-side faceplate. You do not turn that box into a decorative plate and keep the same object. B004TRRV48 is an 86 mm screw master for an accessory box of at least 25 mm. A BG trade sheet prints 35 mm. It is not an NTE5c. The black nickel master, B00KCYLMWO at £5.99, does not say NTE5 and does not state the terminals. The antique brass master, B07KGHMVKB at £11.72, is also a screw master. Its 13 A and Wi-Fi lines are a conflicting block. B07WR6YBZ7 at £9.95 is an NTE5c faceplate only. B0CPD1DG9B at £14.20 is sold as an NTE5a, and its back box is a bullet. Neither is a bedroom extension. The 1STec kit, B08L6G7XZJ, is an extension of about 68 mm. It will not replace the split NTE.

Which kept listing is which

Entry masters are B004TRRV48 (white screw, £5.99), B00KCYLMWO (black nickel, £5.99, terminals not stated), and B07KGHMVKB (antique brass screw, £11.72). Master-side faceplates are B07WR6YBZ7 (NTE5c, £9.95) and B0CPD1DG9B (NTE5a, £14.20). Secondaries are B004TRRVA2 (white screw, £3.89), B0CJQFSMZ9 (white faceplate, £11.20, terminals not stated), and B08L6G7XZJ (68 mm kit, £8.95). Every secondary assumes a master already exists. A colour match does not change the role. Other reasons to skip a row are on the best telephone socket page. Prices are amazon.co.uk figures from 16 October 2026. A qualifying purchase can earn a commission at no extra cost to you. There was no lab test.

Common questions

Can a secondary be the only socket?
No. The BG 8BTS listing says you use it with a master, as an extra point. The 1STec kit is an extension with a back box, not a lead-in. If the only plate has failed, replace it with a master or the correct NTE faceplate. The cheaper white plate is not that replacement, even though the face looks the same.
What is wrong with two masters?
A second master puts master components on an extension. The archived OFTEL code says a master used as an extension can upset the system. It also gives you a plate that looks like the network end and is not the test socket. Trade pages that mention a second master as a bell-wire cheat are describing a workaround. Keep one master, and fix terminal 3 if the bells are the issue.
Is a black nickel master an NTE5?
No. B00KCYLMWO is a single master in black nickel, at £5.99. The file does not mention NTE5, a test socket, or a terminal type. The NTE parts in this set are the NTE5c faceplate B07WR6YBZ7 and the NTE5a listing B0CPD1DG9B. A decorative master can sit on the customer side. It is not the network plate, and a later visit can put the Openreach front back.
Is the 68 mm kit a master?
No. B08L6G7XZJ is a surface extension, about 68 × 68 × 29 mm including the box, with an IDC tool. thinkbroadband treats that size as an old socket or an extension, not as the 85 mm split NTE. It will not cover an NTE. Use it when a master is already fitted.
I only have two wires. Do I buy another master?
No. Two wires can be the speech pair, with the bell wire missing, which can leave extensions quiet. That is terminal 3 on the fitting page. A second master is the wrong spare. If you cannot find a split master anywhere, ask the provider before you add a master at a remote point.

Related pages

Telephone socket

Best telephone socket: match the hole, not the stars

Telephone socket buying guide: role, then terminals

Telephone socket on full fibre: often the wrong buy

How to fit a telephone socket on the customer side

Sources

Public UK sources on the master socket, BS 6312, and the digital landline switch. Listings checked 16 October 2026. Prices on amazon.co.uk move.

  1. Openreach copper handbook (retrieved 16 October 2026)
  2. Openreach new-sites wiring, August 2024 (retrieved 16 October 2026)
  3. Openreach PSTN switch-off (retrieved 16 October 2026)
  4. GOV.UK telecommunications modernisation timeline (retrieved 16 October 2026)
  5. Ofcom, future of landline calls (retrieved 16 October 2026)
  6. Ofcom, broadband and landline faults (retrieved 16 October 2026)
  7. BSI BS 6312-1:1994 plugs (retrieved 16 October 2026)
  8. BT Digital Voice setup (retrieved 16 October 2026)