Adding a Second Line to Your Existing Phone Jacks
Underlined Italics = a future hot link to additional information
As a telephone technician, the question I am asked most often is:
"How do I hook up the wires to add a second phone line in my house?"
This page is intended to provide the answer to that question,
with information and diagrams to help you connect the wiring in your home.
My advice here is aimed towards connecting both your existing line (Line
1) and your new second line (Line 2) on new or existing jacks at the locations
of your existing jacks.
This will provide you the most flexibility in determining how to use your
expanded phone service.
This advice is only applicable if your phone cable is normal station cable with
two or more pairs of wire.
Most people will be able to add a second line to their existing jacks
without installing any additional cable. Two wires (one "pair") are needed
for most phone line connections.
Normal station cable (what your phone tech may call "JK") used for residential
installations has four wires (two "pair").
Single line installations only use one pair, leaving the second pair available
for the second line.
You may find that your home was originally wired with both pairs connected to
the jacks and is essentially "two-line ready".
If you plan to "do it yourself", I recommend you consider accomplishing
all of your rewiring before actually ordering your second line from the
This work is all fairly simple, but you'll find that it may take more time than
expected to accomplish.
By doing your wiring first, you'll be able to start using your second line when
it is connected by the phone company.
This will also permit you to request professional assistance, if needed, before
you start paying for a second line that you would not be able to use until the
jacks are rewired.
However, you should contact your phone company to
ensure that additional line service will be available when you are ready to
order it before proceeding with rewiring your jacks.
In the following advice, I have referred to the wires by color.
If your cable has more than two pairs, the colors will be different.
See my pageon Wire Color Codes to translate the
colors of your multiple pair cable.
You may also want to look at my pages on
Wiring a Third Line and
Wiring for DSL.
Step by Step Advice for Wiring for a Second Line
Step 1 - Check in the customer side of the NID.
Ensure that the green and red pair of your cable is attached to the screw
posts for Line 1.
Confirm that the black and yellow wires are available but not connected to
If they have been clipped, see my advice about
reworking your entrance cable.
If you find that your black and yellow pair is in use, the green and red pair of
your cable may be defective.
In most cases, if your station cable has only a single pair or has a defective
pair, I recommend obtaining professional assistance, unless you want to
install new cable yourself to add the second line.
Step 2 - Determine how you want your
jack connections wired.
You may need to obtain new jacks or special adapter plugs.
You haveseveral options on how to connect your jacks:
Step 3 - Examine the routing of your phone cable
to determine where all junctions exist.
If you find junctions, ensure that all wires of the same color are connected
You may find that the black and yellow wires were not previously connected at
If you need to rewire junctions to connect the black and yellow wires, you may
wish to use a junction block.
Jacks may also be a junction location.
I recommend using an ohm meter to perform a continuity check of the pair between
each junction location and your wires at the NID.
Line 1 and Line 2 on one jack (easiest
way to use "two-line" phones and may allow use of single line phones on
existing jacks with adapters)
Line 1 and Line 2 on separate jacks (easiest
way to use your existing single line phones)
Both of the above (this is what I recommend
- provides the most flexibility without using expensive
Step 4 - Open your existing jacks and ensure that cable with two pairs
is routed to each jack.
You may find that a jack is used as a junction point, with multiple cables
attached to the same jack.
Rewire each jack according to the jack connection
method you selected in Step 2.
Step 5 - Test your work. In the customer side of the NID, connect the
black wire to the same screw post as the green wire and the yellow wire
to the same screw post as the red wire.
Use a known good phone and ensure
that you can get dial tone and place a call at each jack for Line 1 and
Disconnect the black and yellow wires in the customer side of the NID.
Step 6 -Contact your phone company and order
your second line.
Step 7 - The phone tech that installs your second line at the NID may
or may not connect the black and yellow pair to the second line in the
customer side of the NID.
If not, connect the black wire to the green screw post of Line 2 and the yellow
wire to the red screw post of Line 2.
Step 8 - Plug in phones on your jacks for line two and begin enjoying
your expanded phone service!
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