RJ45 to BT phone...

Discussion in 'UK VOIP' started by Paul Ockenden, Sep 11, 2005.

  1. My Fritzbox has an RJ45 on the back which can connect to either analog
    or ISDN phone lines. It comes with an rj45 - rj45 lead, plus some adaptors
    for the German phone system... useful!

    Does anyone know the wiring I need to connect this RJ45 socket to a UK
    phone line? I did a google, and a search on ebay, but apparently there's an
    issue of primary or secondary, full master or not, etc. All a bit beyond me!


    Paul Ockenden, Sep 11, 2005
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  2. Paul Ockenden

    7 Guest

    Almost any telephone shop has the adapter for it.
    Old modems had the adapters so you might look in an old box
    or a discarded card and find it still there.
    7, Sep 11, 2005
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  3. Paul Ockenden

    Ian Guest

    Hi Paul
    If its using the standard pins or RJ45 which are 4 and 5, You will need a
    Master Adaptor , Sometimes called PBX Master
    such as

    Ian, Sep 11, 2005
  4. Paul Ockenden

    Lurch Guest

    Close, but no cigar. Wrong way round that one.

    I'd make my own lead so I'm struggling to find a pre-made adapter
    anywhere. You should be able to just stick a normal BT-RJ11 lead in
    from any standard analogue modem.
    Lurch, Sep 11, 2005
  5. Paul Ockenden

    Ivor Jones Guest

    "Paul Ockenden" <>
    wrote in message
    If it's the analogue/ISDN port it uses pins 1 and 8, the outermost two,
    it's a non-standard pinout arrangement.

    Ivor Jones, Sep 11, 2005
  6. Paul Ockenden

    Teal'c Guest

    Teal'c, Sep 11, 2005
  7. Almost any telephone shop has the adapter for it.
    I thought old modems used RJ11s, not RJ45s...

    Paul Ockenden, Sep 11, 2005
  8. Paul Ockenden

    Lurch Guest

    They do, as do new ones too. An RJ11 plug will fit in an RJ45 socket
    though, but as someone else has pointed out in this thread, pins 1+8
    are used so this wouldn't work as RJ11's only go up to 6 pins. They
    also have a tendancy to malform pins 1+8 in the RJ45 socket too,
    Lurch, Sep 11, 2005
  9. Paul Ockenden

    Lurch Guest

    If you can't source an adapter for this then drop me an email and I'll
    make you one.
    Lurch, Sep 11, 2005
  10. Paul Ockenden

    Peter Parry Guest

    Centre two on the RJ45 to a master socket (or PABX master) pins A and
    B or 2 and 5 (depending on how it is labelled). 2 and 5 on a slave
    will work but you may get no ringing signal on the phone.
    Peter Parry, Sep 11, 2005
  11. Centre two on the RJ45 to....

    Now I'm confused. One of you says use the centre pins, another
    says the outer pins....

    Paul Ockenden, Sep 12, 2005
  12. centre is the standard, so you can use an RJ11 phone plug into RJ45

    Outer two is what the Fritzbox thing is using ie its non-standard.

    Phil Thompson, Sep 12, 2005
  13. Paul Ockenden

    Ian Guest

    Hi Paul.

    The standard for a phone onRJ45 is the center pins, But the socket you refer
    to is a dual use, Both ISDN and POTS. so it would make sense to use 1 and 8
    but who knows.

    I would raise a support call with AVM if I were you. Or get your meter out
    and see what is happening on pins 1 and 8

    Ian, Sep 12, 2005
  14. Paul Ockenden

    Ivor Jones Guest

    My Fritz!Box definitely uses 1 & 8, I can see it in the plug. It's a
    different model to Paul's though so it may be different wiring but if the
    socket has the same purpose it's unlikely.

    Ivor Jones, Sep 12, 2005
  15. Paul Ockenden

    Peter Parry Guest

    The nice thing about standards is that you have so many to chose
    from. To connect to the phone socket (not the phones - they use
    RJ12) the Frixbox as I understand it has an RJ45 cable designed to go
    directly into an ISDN RJ45 connector or (with an adapter) to plug
    into an analogue RJ11 wall socket.

    The RJ USOC (see below) numbering scheme applies to
    telecommunications circuits, data networks are different. Under USOC
    RJ11/12 wiring puts the analogue signal on the centre two pins of the
    plug (3 and 4) (RJ11 is numbered 2,3,4,5, RJ 12 is 1,2,3,4,5,6) and
    the centre two pins of an RJ45 connector (pins 4 and 5) (RJ45 being
    numbered 1-8).

    ISDN wiring would put the first pair (terminal equipment transmit) on
    RJ45 pins 2 and 5 and the second pair (terminal equipment receive) on
    pins 3 and 4.

    Ivor Jones has written that the Fritz connector is non-standard and
    uses pins 1 and 8 for the analogue and a hunt around www.dslteam.de
    shows he is correct. These pins are spare on an ISDN connector and
    Fritz have obliviously used them for the analogue connection to avoid
    the need to sense the network type. In this case go from 1 and 8 on
    the Frieze to 2 and 5 on a BT plug (the outer pins).
    Peter Parry, Sep 12, 2005
  16. Paul Ockenden

    Ivor Jones Guest

    Hmm, now this is where it gets interesting. The cable supplied with my UK
    spec. Fritz!Box has an RJ45 (pins 1 and 8) wired directly to a standard BT
    plug. The instructions supplied say that this can be plugged directly into
    *either* an analogue phone socket *or* an ISDN connection. Now I have
    never used ISDN but I have seen photographs of the terminal equipment and
    aren't they standard phone sockets..?

    Ivor Jones, Sep 12, 2005
  17. Paul Ockenden

    Lurch Guest


    Well, yes, kind off. ISDN is generally presented on RJ45 connectors
    via something like an NTE8 (littleish grey box). The ISDN Home and
    Business Highway services supplied ISDN on the RJ45 sockets but as
    part of BT's equipment also had a terminal adapter (large white box
    with 2 blue RJ45's and 2 BT sockets) which effectively converts ISDN
    to POTS, hence the provision of standard BT sockets on an ISDN
    service, which aren't actually ISDN, just standard analogue ports.
    Lurch, Sep 12, 2005
  18. Paul Ockenden

    Peter Parry Guest

    No, ISDN uses RJ45 and (after the BT Network Terminating box) two
    pairs of wires all of which are required. Using the 1/8
    configuration for analogue means that using their supplied cables you
    plug RJ45/RJ45 for ISDN and BT/RJ45 for analogue and can't get it
    Peter Parry, Sep 12, 2005
  19. Paul Ockenden

    Marc Popek Guest

    Marc Popek, Oct 10, 2005
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