Modem line cords and telephone line cords

Discussion in 'DIY Computers' started by Lem, Jul 8, 2007.

  1. Lem

    Lem Guest

    By "line cord" I mean the length of cable between the telephone wall
    socket and the socket on the telephone instrument itself. Of course all
    this is for the UK.

    (1) Am I right in saying that the plugs are each end are called "BT
    431A" and "RJ11" respectively?

    (2) If I take a line cord designed to attach a modem to a wall socket
    and I use it to attach my telephone then my telephone does not work.
    Why is this? Is the modem line cord wired differently, are there fewer
    wires, or are there some minature resistors?

    (3) Is there a difference between (i) the modem line cord used to
    attach (i) a modem to a wall socket and (ii) a modem on a PCI card to a
    wall socket.
    Lem, Jul 8, 2007
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  2. Lem

    Gaz Guest

    I have come across BT branded phones (who should know better), which use a
    none standard wiring for connecting their headsets to the phones, and the
    phones to the wall. The cables look like standard rj11s but arent wired as

    Gaz, Jul 8, 2007
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  3. The message <f6qvds$hl8$>
    Most modems (whether internal or external) have their RJ11 line cord
    socket wired according to the yank standard (middle two pins, 3 and 4 of
    the 6 contact stations numbered from left to right, or from right to
    left, depending on your PoV :) and connecting to the BT plug on pin
    contacts 2 and 5 (same left to right, or right to left sequence as the

    These line cords, therefore, aren't wired in the straight pin for pin
    arrangement used by UK telephone handsets (and fax or answer machines)
    and are incompatable for the vast majority of modems. However, there
    were a very small number of (usually external) modems that _were_ wired
    the same as a telephone handset designed for the UK market.
    Johnny B Good, Jul 8, 2007
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