Modem line cords and telephone line cords

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.

 

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
standard.

Gaz

 

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
RJ11).

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.