Does my telephone have a master socket or two?

16 Aug 2012
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United Kingdom
Good Afternoon All,

I have the following setup in my telephone:

bt line comes in, and goes into rectangle box - inside has AB screw terminals, and 1-3 wire push type connectors.

All 5 have wires in them.

From the 1,2 and 3, goes to my first telephone socket, which looks like an old style master to me, into 2,3 and 5...

Question then is, which is the "master socket" the rectangle box or the first phone socket.

If i take the first socket out and join further telephone sockets to this, is it ok? (ie instead of having rectangle box to telephone socket,
rectangle box, to junction box, which has two telephone sockets from it?)

Also as there is broadband in the house, there are filters for the telephones etc. If my house alarm is wired directly into the telephone wiring (2 and 5 on phone socket go to a and b on alarm panel/dialer) would i need to cut a filter into place in some form?
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The first phone socket is the master.

You must extend from that using a plug which can be disconnected.

Simplest (but not legal) would be to replace the rectangular box with a NTE5 and change the existing master socket to an extension. You would need an NTE5 backplate with screw terminals for the incoming drop wire, eg

This has unfiltered terminals for the front plate as well if you need to run an unfiltered line to the modem.

The burglar alarm must have a broadband filter on it unless you use a filter at the NTE like the one linked above. You can get hardwired filters eg
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Is there anything wrong with connecting the standard 431A connector into the socket, and soldering the other end to various other wires to other sockets? or should they be connected using the proper connectors?
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Did a bit more digging around, the rectangle box is a filter of some description, and so the telephone socket is quite rightly the master.

The wiring that was done in the house however didn't use this as the master! All other sockets were bypassing it so I had to require a little, put a NTE5 box, from the filter, and then at present just used a normal single unfiltered front, and from there connected in the rest of telephones in the house from there.

Ran a single wire from the front to a connector block where I then had 4 or 5 other wires from the other sockets coming in.

All works and i guess is a bit more "legal" now... just had to do it illegally to get it right.

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