Changing diamond cable point for master socket

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Feb 22, 2024
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Hi all,

I've just decorated my living room and wanted to switch out the old diamond cable point for a new master socket but the wiring within the socket is 25 years old and I'm a little lost on it.

Could anyone give me any pointers on which points should be connected?

I've got a few years experience as a sparky but it was about 15 years ago so my knowledge of phone connections is pretty fuzzy.

I've attached a couple of images of the diamond cable socket and the new socket.20240222_095312.jpg20240222_095304.jpg20240222_095255.jpg

Thanks in advance, I appreciate any help given
Check all phones, do they have dial tone?

Have you still got a means of testing voltage?
(Old socket) Check the blue/white blue/white on terminals marked A and B I will guess it's 50v
(New socket) If so, connect these to 2 & 5 (doesn't matter which way round)

Check other extensions in house, they should all be dead.

If they are, connect the blue/white and white/blue (from old socket) to same colours on new socket.
all phones should now have dial tone, but will not ring when called.
Connect orange/white to terminal 3
All should now work*

Until BT change you to fibre broadband, when none of your phones will work.

Terminals 2 & 5 are your main connections for the line. The actual colours used may or may not match with common good practice..

But the traditional order of using the pairs in a 3-pair, (6core), telephone cable are-
First: Blue/White - White/Blue
Then: Orange/White - White/Orange
Next: Green/White - White/Green

If larger cables then goes onto Brown/White, Slate(grey)/White........ Blue/Red, Orange/Red, Green/Red, Brown/Red, Slate/Red... etc.. etc..

Historically polarity could be an issue with some devices.. (e.g. some fax machines / answering machines got a bit confused with the incorrect polarity),
but most modern phones will still work even with the line reversed from the standard.
Brill thanks for your advise guys, I'll take another look at it today and should be able to get it sorted pretty easy now.

To be honest I don't even have a landline it's more for if we ever sell the property.

Thanks again for the help
Orange (3) is bell so not really necessary 2&5 line The polarity these days is not so important. The old Trim phones were polarity conscious! As an aside BT don’t like people messing with the master box and have prosecuted in the past. The new master boxes have a clamp system for the cables.