UK Telephone <-> Structured wiring

I'm still trying to clear up the ins and outs of this in my mind, and I'm wondering if you all can help me make sense of all the fragments of info I've gleaned.

1) Does modern UK POTS equipment *require* the bell shunt wire, or will most work without?

2) I see that for standard analogue phones, they are a generally a three-wire system, that may also use an earth line. When is this earth line used and how common is it?

3) Apart from the extra pair of wires on the outer pins, are PBX extensions compatible with standard extensions? Can you plug a standard handset into a PBX extension socket?

RJ-45 to BT-431/631 converters:

4) I read that there are three types, although the terminology seems flexible. The secondary/slave type is the most obvious, and I've worked out how those are wired. When would you use this type?

5) There also seems to be a standard master type. I imagine internally that this takes the A and B lines (on the blue pair in the Cat5) and contains the surge protector, test resistor and bell capacitor to provide the third bell wire. Is this correct? When would you use this?

6) What is the third type?
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suggests that it is a "PABX master".

7) The secondary/slave adapter that I examined disagrees with the wiring on the above page. Mine has earth (4 on the BT socket) going to 2 on the RJ-45, whereas his has it going to 1. Which is correct, or are there different way to do it?

8) I have an incoming standard analogue line with a BT socket and I need to route it via the structured cabling.

Should I do:

(A) BT #5 -> RJ45 #5 (B) BT #2 -> RJ45 #4

And put a master adaptor at the remote end? Will it matter having two master sockets as it were, wired to the same line, e.g. in terms of the impedance viewed from the other end and the test resistor?

Or should I do as above plus:

(bell) BT #3 -> RJ45 #1

and use a secondary adaptor at the other end?

Sorry for all the questions! Hopefully someone can help me with some of them.

Reply to
John Carlyle-Clarke
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In article , John Carlyle-Clarke writes

Some will, some won't. :-( Most FAX machines, and modems will be fine on two wires. Most modern answering machines seem (in my experience) to cope as well. Telephones are a lot more variable, and many will not ring on just two wires.

The so-called earth is mainly used on older PBX systems. - Older POTS used it, but is now (almost) extinct.

*I will now be flamed by thousands of people using the earth.* ;-)

If you mean is the extension wiring 'pin for pin', then yes. If you mean will an analogue POTS phone work on a PBX, then maybe. - But ONLY if the port on the PBX is an analogue port. Many 'PBX phones' use a digital system to carry both the voice and signalling from telephone handset back to PBX. Some use one pair for analogue voice, and a second pair for signalling.

Yes, there tend to be three common types.. how they are wired depends (a little) on who manufactures them. Molex, for example, do *many* variations, to suit various 'PBX' systems.

My rule of thumb for 'unknown' PBX systems, is to try a slave first. - They tend to be a little cheaper, and there is less to be got wrong!

A 'PSTN', or 'Full Master', has all the components to make a 'proper' POTS connection from two wires. - so it should have protector, resistor, and bell capacitor in it.

A 'PBX/PABX Master' will (normally) only have the bell capacitor in it.

See answer above, about different makes!!

I would do it this way;

Wire blue and orange pairs from the customer-side of the BT master, to the corresponding pairs on a spare RJ45 outlet. - If you have a patch panel, quite often there are used jacks. Or have a dedicated panel for 'voice services'. You can then use ordinary patch cords etc. and secondary adapters everywhere. I also quite often wire a group of three or four jacks in 'parallel' across the back for the first two pairs. All pin 1's together, all pin

2's, all pin 4's and all pin 5's. - This assuming 568B wiring pattern. Then if you need a POTS line in two, or more, places just patch into this parallel strip. The remaining two, or three sockets then all have the same service on them. This will NOT work with PBX systems, as each telephone needs it's own signalling etc.

That's what we're here for!

HTH, Philip Partridge

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