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- Xref: sparky comp.dcom.modems:19328 sci.electronics:22460 uk.misc:2518
- Path: sparky!uunet!pipex!bnr.co.uk!uknet!axion!apricot!marcusj
- From: marcusj@apricot.co.uk (Marcus Jenkins)
- Newsgroups: comp.dcom.modems,sci.electronics,uk.misc
- Subject: UK phone circuits vs. US phone circuits
- Message-ID: <C0oMBu.BC@apricot.co.uk>
- Date: 11 Jan 93 08:59:51 GMT
- Organization: Apricot Computers Limited
- Lines: 115
-
-
- I need some clarification of UK telephone circuits
- and how they map onto US ones. I have just bought
- a UK-US telephone adaptor, but when I opened it up
- to have a look at what was connected to what I got
- rather confused. Here's how it's connected:
-
- First let's get a common reference for the
- connectors:
-
-
- ---------
- | | An illustration of a US 'phone
- --- --- connector in my best freehand
- | | ASCII. (Looking at the open
- --- --- end of a socket).
- | |
- | |
- | |
- | |
- | | | | | | | |
- -----------------
- 6 5 4 3 2 1
-
-
-
- 6 5 4 3 2 1
- ----------------||| An illustration of a British 'phone
- | | | | | | | ||| connector. (Looking at the top of
- | | | | | | | ||| a plug.
- | | | | | | | |\\
- | | | | | | | | ||
- | | | | | | | | ||
- | ------------- | \\
- | ------------- | ||
- | | | | | | | | ||
- | | ||
- | | \\
- | | \\
- | ----------- | \\
- | | | | | | \\
- | | | | | | \\
- | ----------- | \\
- | |
- -----------------
-
- What my adaptor does is:
-
-
-
- UK plug US socket
-
- BT ID pin pin label in socket
-
- A wire 5 ------------- 4 T1 (tip cct. 1?)
- B wire 2 ------------- 3 R1 (ring cct. 1?)
-
-
- Do all US circuits really only have the 'tip'
- and 'ring' connections? (I have looked at the
- 2nd Edition of 'The Art of Electronics' by
- Horowitz and Hill and can't see anything to
- the contrary.) Why do we (in the UK) need 2
- or more wires to do the same job? This especially
- of concern when I was under the impression that
- you *can* (as opposed to *may*) connect your
- average modem, for example, that you buy in the
- US to the British 'phone system and it will work.
-
- In the BT circuit there is a local earth and a
- shunt wire connection (on 4 and 3 respectively of
- the BT plug). In the US 'phone socket box for the
- adaptor described above, there are also the GND
- and AUX connections (on 5 and 2 respectively).
- Why aren't the grounds connected through in the
- adaptor? What is the 'shunt wire' connection in
- the Uk circuit (and how is that different from the
- AUX connection in the US circuit?)
-
- As you may have guessed all of this is to find
- out how to connect a US modem to the UK 'phone
- system. As far as I know people have done this
- and it works. I assume that the adaptor I have
- described above will do the job. However, the
- fact that it appears to be rather minimal is a
- bit worrying.
-
- I am quite aware of the British BABT 'phone
- apparatus approval system which makes it
- illegal for me to connect non-BABT approved
- equipment to the British 'phone system directly.
- Therefore consider my enquiry as purely a
- hypothetical excercise. I would never dream of
- breaking the law (however petty it might be and
- even if it was produced principally in the
- interests of preserving vested interests of a
- fat monopoly like BT (and of course to prevent
- bozos from connecting the mains at 240V into
- the 'phone system which is what I expect anybody
- from BT will tell you was the sole reason)
- - flame off).
-
- Thanks in advance.
-
- Please mail me.
-
-
- _ _ _
- ' ) ) ) Internet: marcusj@apricot.co.uk
- / / / __. __ _. . . _ UUCP: marcusj@apricot.uucp
- / ' (_(_/|_/ (_(__(_/_/_)_ If all else fails from US, try:
- Marcus Jenkins apricot!marcusj@relay.EU.net
- Tel: +44 21 472 3002 Fax: +44 21 471 2935
- Disclaimer: Anything I wrote above is, of course, my own view and
- does not in any way represent my employer.
-