I am wanting to connect the front of the master telephone socket (the one that generatate the ring) to the back of a general socket. I have connected the red and white to terminals 2 and 5 which works, however I have lost the ring. How do I connect it to work normally?
You need to connect terminals 3 and 4, also.
Or buy a new phone. Many will ring on 2+5 only, and it provides better sound quality to disconnect the ring line, which is unbalanced.
Christian.
Only 3 is actually required as this is the shunt wire (bell). 4 is a local earth not used much - if at all - these days. Think it was for party lines.
I'm not sure about the quality issue? It's possible the bell wire might make a difference on an ADSL setup, but I'd say probably not in a normal domestic setup.
However, most cordless phones don't use the ring circuit anymore.
"Dave Plowman (News)" wrote | Only 3 is actually required as this is the shunt wire (bell). | 4 is a local earth not used much - if at all - these days. | Think it was for party lines.
It depends on whether you follow the BS or BT numbering whether the ring is on 3 or 4.
The earth was used for earth recall on PABX. Line jack units were never fitted on party lines.
Owain
Interesting. What's the BS numbering? And did it apply to domestic installations?
Ok.
By a masterpiece of technical superiority, between them the BSI and BT managed to number the 431A plug in the British Standard as a mirror image of the socket, so when inserted pin 1 on the plug goes to pin 6 on the socket, pin 2 to pin 5 and so on.
The pin numbering isn't shown on the plug but many packets of plugs in the DIY sheds come with a little diagram on the back which often follows the BS numbering.
If you do the logical thing and put a plug on assuming the numbers are as on the socket the phone may not ring. Just to confuse the issue further some imported sockets also invert the numbering so if you wire pin 1 on an NTE5 master socket to pin 1 on a Chinese (insert shed name here) socket it may well be going to 6 :-).
A simple way of remembering the correct orientation for the BT plugs if you like mnemonics is Ring on the Right. When you are holding the plug with the latch on the right the ring terminal (4 on the plug, 3 on the socket) is always just right of centre.
I think this is a reference to the fact that the numbering of the LJU IDC (or screw) terminals runs the other way round to the pin numbering of the connector itself - see table below. Why they did it like that has always been a mystery to me. Maybe it was just a c*ck-up on the part of whoever laid out the first PCB and we're stuck with it.
LJU IDC connector terminal pin no. function
-------- --------- --------
2 5 B-wire 3 4 ringer (B-wire via 1.8uF cap in master) 4 3 earth (when used) 5 2 A-wirePin 6 of the connector is the one nearest the release lever. A quiescent line has its A-wire at approx. earth potential and its B-wire at -50V.
So the answer to the question that has been a mystery to me for so long (see my other post) is that the connector pin numbering came from a BSI committee whilst the LJU terminal numbering was determined by BT, and the two didn't talk to each other. (I.e. it was a c*ck-up.) Is that right?
All useful info, saved for reference, thanks. Of course none of this would have happened if the numbering had been got right in the first place. Plus ca change...
Whether they didn't communicate or (as I suspect) someone omitted to check the draft specifications in detail I have no idea. Apparently it wasn't noticed for some time.
It was certainly that.
I thought BT (or was it the PO?) designed the connector in the first place, and it was later "adopted" by the BSI.
Now that I can believe.
That too - and by then it was too late...
Pass - although ISTR Vero Electronics being involved in the design of the connector.
I'm pretty certain it came in GPO times - as did System X etc. Privatization was so successful because of those publicly funded development costs, which must have been large.
The problem is that when you run extensions with quality twisted pair cable, the signal (2+5) is pretty good, with good interference rejection etc. When you add the bell line, this signal is unipolar and very subject to crosstalk and interference, which then gets injected back into the signal, causing problems.
Obviously, with small extensions and a quiet electro-magnetic environment, this is often not detectable, but it can become quite troublesome if neither applies.
Christian.
This is avoided by connecting only 2 and 5, and using master sockets for all extensions too. If you have multiple phone lines in the same cable bundle, this is pretty essential or the ring signal on one line will be quite audiable on other lines. This would only cause problems with any lines using multiple old phones with real bells and pulse dialling, where dialing on one phone can cause bells in the other phones to 'tinkle'.
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