TELECOM Digest OnLine - Sorted: Re: Wiring Two Lines on One Jack

Re: Wiring Two Lines on One Jack

John Beaman (
Fri, 11 Mar 2005 08:55:16 -0600 wrote to inquire about Wiring Two Lines on One Jack
on 10 Mar 2005 19:21:37 -0800:

> Hi,

> I would like to wire one jack for two lines. Here is the setup of the
> wires after opening the jack.

> The red screw terminal has two blue and 1 orange wires connected to
> it. The green screw terminal has 2 white/blue and 1 white/orange wire
> connected to it. I'm just curious as to why there are 3 wires
> connected per terminal.

> The yellow an black screw terminals are not connected to any
> wires. Now what should I do to be able to access a second line?

> Thank you!


Sounds to me like your residence is wired with CAT3 (4 pair) cable
instead of the old standard wiring used for phone jacks. It would
also seem that your phone jacks are "daisy chained" together instead
of each being wired directory from the demark (star topology). I am
also assuming that the orange pair is wired to the terminals because
there is an open in one of the blue pairs, and someone just grabbed
the next available pair as a workaround. Or, they could be used as
some sort of intercom / door access system. Please see the attached
chart documenting the relationship

Standard wire Cat 3

Tip- Green -----Line 1----- Blue
Ring- Red -----Line 1----- White/Blue stripe
Tip- Black -----Line 2----- Orange
Ring-Yellow ----Line 2----- White/Orange stripe

With that in mind, there is no reason you cannot use the green or
brown pair for your second line. Provided that they are not in use at
any other jacks. I would highly recommend opening up the other phone
jacks, and see if you can find another jack where the orange pair is
in use. While that would not be conclusive, it would further
substantiate my guess about the orange pair being used in place of the
blue pair.

The Evangelical Lutheran Good Samaritan Society.

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