Telephone Jacks and Wiring

Information is given on telephone wires
and jacks, and instructions how to
connect the wires.

Telephone Jack Wiring
And Repair

How to wire a telephone jack.

Telephone Jack

Telephone Jack

The above picture shows the back side of a
common telephone jack used today in the
home and business. The telephone jack has
six colored wires, green, red, yellow, black,
white, and blue. For a single telephone
number only the green and red jack wires
are used. If there is a second telephone
number added onto the jack for a two line
telephone, it is connected to the yellow and
black jack wires. If the jack wires has a
white and blue wire, they are used for
special applications.

Telephone Wire Colors Codes

Older Three Conductor Wires

Red - (Ring) - first line

Green - (Tip) -first line

Yellow - was used for ground in a
multi-party line setup

Older Two Pair Conductor Wires

Green -(tip) - first line

Red - (ring) - first line

Yellow - (tip) - second line

Black - (ring - second line

Four Pair Conductor Wires
White with blue marks (tip) - first line
Blue with white marks (Ring) - first line

White with orange marks (tip) - second line

Orange with white marks (ring) - second line
Usually designated for ADSL, if no second
line is used.

White with green marks (tip) - third line
Green with white marks(ring) - third line
Usually designated a spare, or for a fax line

White with brown marks, spare
Brown with white marks, spare

Dual Telephone Jack

The dual line jack is used where two
separate telephone numbers are required
at one telephone jack. Each separate
telephone line is attached to the red and
green wires of each separate jack
connection. The white/blue wire of the set
run wire connects to the green wire of one
side of the dual jack. The blue wire of the
set run connects to the red wire of the jack.
The white/orange wire of the set run
connects to the green wire of the other side
of the dual jack. The orange wire connects
to the red wire. This jack is wired to have
two separate telephone numbers at the
dual jack.

To have both sides of a dual jack have the
same telephone number, bridge with a
jumper wire, one half of the dual jack to the
other. Green to green, and red to red.
Connect the w/b of the set run to the green
of one of the jacks, then connect the blue
wire of the set run to the red of the same
jack. Both sides of the jack will now work
with the same telephone number.


No matter what kind of jack, all the jack
wiring is the same, center two pins are
telephone line one.

Troubleshooting and Repair

90% of telephone noise occur at the
telephone jack and telephone. Unplug the
telephone set cord from the wall jack and
check the mini plug end for corrosion.
The tiny pins should be shiny clean gold in
color, any green or black indicates corrosion.
If there is corrosion, both the set cord and
wall jack need to be replaced.

Telephone surface mounted jacks are
located low on the wall where they are
susceptible to water damage when rugs
are steam
cleaned, the water-soap over spray ends up
in the telephone jack. Also wall washing can
cause water/soap to end up in the jack
causing corrosion. The worst cause of
telephone jack corrosion is caused when
people hang wall paper, the water and glue
mixture is extremely damaging, because
the conductivity of the glue is very high
causing corrosion in a very short period
of time.

Going Further

When there is no dial tone, the first step to
troubleshoot a telephone no-dial tone
trouble is to determine whether the trouble
is inside the home or out side. Go to the
network interface box on the side of the
house, this is the telephone companies
de-marcation point. The wires toward the
central office are the telephone companies
responsibility, the wires toward the house
are yours. Using a Phillips screwdriver open
the lid of the grey plastic interface box.
If the type of interface has a short
telephone cord plugged into a telephone
de-marc jack, unplug this cord and plug a
telephone set into it. If you can get dial
tone at the interface box, but not in the
house, the telephone trouble is in the
house and is your problem.
If there is no dial tone at the interface box,
the trouble is the telephone companies.

Go Further

If you determine the trouble is somewhere
inside the house, the best way to go
further is with the use of a multi-meter.
Set the meter to read ohms on the X1
scale, remove all the jack set runs
(individual wires to each jack) and isolate
them from the binding post.
Take a separate reading on each wire pair,
a short (full deflection of the meter
needle) will indicate the problem wire.
Tie all the other set runs down on the
binding post, and plug in the de-marc jack
at the interface box. Check all the jacks in
the house for dial tone, the jack that
has no dial tone
is the one with the
problem. Investigate this jack further,
remove the telephone and recheck the wire
for a short. If there still is a problem, tie
down the wire for this jack run at the
interface box, try changing the jack, if this
does not help, the trouble is in the wire
between the interface box and the jack.
Usually 90% of the time it will be a bad
jack because of corrosion, or a telephone

Hum on the Line

Hum at the telephone, means there is a
path in the telephone wires to earth ground,
this usually is caused by damaged wire
coating, and wetness around the wire,
either in the home or between the home
and the telephone central office.

AC Hydro power inducting onto the line
can also produce a hum. Normally the
telephone lines between the telephone
central office and your home are in balance,
any hum in the line is removed before it
reaches the telephone set. Poor bonding of
the ground sheath around telephone
wires in telephone cables, can produce a
hum. If you live in a rural area, with long
wire runs of aerial telephone cable near
hydro power cables, a hum is more apt to
happen. Usually when the telephone wires
are out of balance because of poor
grounding, the telephone wires will
sometimes pick up a weak radio signal in
the background. If the hum in the line
cannot be corrected, a noise filter can be
placed at your telephone set, to remove
the hum and any faint radio station.

Static on The Line

Pick up the receiver on your telephone and
dial any single digit, other than zero, this
remove the dial tone. While listening in the
handset receiver, wiggle the set cord near
the telephone jack and at the telephone.
If there is a poor connection, you will hear
static. Also wiggle the handset cord at both
ends of the handset cord, while listening for
static. If you can hear static while wiggling
the cord, the set cord needs to be replaced.

Loose connections and corrosion causes
static in telephones.
Remove the telephone jack cover, and
check that the wires are tightened down

Telephone Protection Devices

A telephone protector is located at the
demarcation device, to help prevent injury
to people, damage to the telephone wire,
jacks and telephone devices in your home,
if and when voltage surges occur outside
the home. This device is situated where the
telephone wires enter the house and is there
to protect you, the home, and phone
equipment. If a large current comes down
the telephone line, its purpose is to direct
the voltage spike to earth ground.

Shocks From Telephone Wires

At standby the telephone voltage is 48 volts,
still shock able, but when the bells are
ringing, the voltage goes up to around 110
volts. You can wear rubber or dry leather
gloves to avoid shocks. Be aware that any
type of shock can upset a pacemakers
operation. If you are standing on a dry floor
or on a rubber mat, there is less change to
get a shock. Obviously, if you are working
on telephone wires in a damp basement,
damp crawl space or under a trailer, there
is more of a chance to get between the
voltage and ground and receive a
major shock.

Alarm Wiring to the
Demarcation Point

Alarm panels are connected to the telephone
wires to send signals to the alarm monitor
company. The alarm panel is set up in a
manner that it disconnects all the telephone
jacks in the home during an alarm trip.
The alarm panel takes full control over the
telephone wire. This is accomplished by
way of a special jack called a jack8.
The telephone wire from the demark point,
is brought to the jack8 at the alarm panel,
and then looped back to a spot where all the
individual jack run wires are located.
The return jack8 wire run connects to all the
telephone jack wires in the house, on a
binding post. The wire from the demark
device is connected to the front two tie
down screws, the wire returning to the jack
runs connects to the two rear tie down
screws. The jack8 provides a loop back,
when the alarm system is not in
alarm mode.

Modem, Router, and
Computer Connecting Instructions

Modem and router
computer modem and router

The Function of a Modem

Modems convert the incoming analog signals
produced by telephone terminals into
digital signals. A telephone circuits bring
the analog signals to a computer modem to
convert into a digital signal for the computer.

Modems also convert outgoing digital signals
to analog (tones), in order to transmit data
over telephone circuits. The modem is a
data set which modulate and demodulate
signals a computer understands.

The modem consists of a power supply,
transmitter, and receiver. The unit contains
a modulator, filtering, wave shaping, and
signal controlling circuitry.

The Function of a Router

A router is required if more than one
computer must share the single modem,
otherwise only one computer can connect
to a modem at a time. The router is placed
between the modem and computers.
A single lead is run from the modem to
the router, and a separate single lead from
the router to each individual computer.
These computers will share the bandwidth
of the internet service. The router manages
the bandwidth between the computers in
use at one time. A small router has four or
five ports, for the computers.

telephone jacks
Hold the connector in your hand with the
retaining clip on the under-side, with the
end pointing away from you. The correct
order of the wires is as follow.
Starting from the left Pin


The White/Green is transmit+
The Green/White is transmit-
The White/Orange is receive+
The Orange/White is receive-

The other wires are not used.


Disclaimer information
and web site policies.

© Serving the Internet Community
Since 1998 - All Rights Reserved.

Plans to Build an intercom

Rotary Dial Telephone

Telephone Jack Wiring
and Repair, at findNchoose.