Planning Ahead When Wiring Your Home or Office
by Brian McConnell
This is a common situation. Someone hires an electrical contractor to
do their phone wiring. They think everything is being done correctly, but
then they find out (after the fact), that the wiring has been run incorrectly.
If you are planning to wire your home or office, this short tutorial explains
how to install your wiring so that you can use any type of telephone system
in the future, either a KSU-less (intercom) system, a key system, or a
PBX or telephony server. If you are hiring a contractor to do your wiring
for you, print this article out and give it to your installer.
"Daisy Chain" wiring - a recipe for trouble
Many contractors will install your phone wiring in daisy chain fashion
unless told otherwise. This causes problems because you have one common
set of wires for all of your phone jacks. This is bad. Many phone systems
require so-called "star" wiring where each phone jack has its own cable
running back to a central wiring point.
Fig. 1. "Daisy Chain" wiring
Installing your wiring to work with all types of systems
The trick to futureproofing your phone wiring is to wire your home or
office in a star configuration. This means that each phone jack has its
own wires running back to a central wiring point. The central wiring point
is either a punchdown block or a patch panel. A punchdown block is a
panel of metal pegs to which the wires are connected. A patch panel is
easier to deal with. It has a bank of RJ-14 modular phone jacks to which
the wiring is connected. Ask your wiring contractor to install a combination
punchdown block/patch panel. This is a punchdown block which has a row
of modular phone/data jacks on the side. This makes it easy to connect
external phone lines, telephone switching equipment, etc., using only modular
phone/data patch cords.
Fig. 2. Star Wiring configuration - each phone jack is independently
wired to the central point.
In homes, KSU-less or intercom systems are very popular. These are also
easy to install and use. They generally use loop or daisy chain wiring,
while more sophisticated systems use star wiring configurations.
If you wire your home or office according to the diagram above, you
can easily reconfigure your wiring from a star configuration to a loop
or daisy chain configuration without rewiring your phone jacks. By making
some minor changes at the punchdown block, you can bridge all of your
phone jacks together for use with a KSU-less or intercom system. If you
later decide to upgrade to a system which requires a star configuration,
all you need to do is to remove some connectors from your punchdown block
to turn these back into separate circuits. Your wiring contractor will
know how to do this.
Types of wiring used by different phone systems
|KSU-less (Intercom) System
|PC Telephony Server
|LAN Telephone System
If you are going through the trouble of rewiring your home or office
for voice, you should have your contractor install a second set of jacks
for high-speed data service (i.e., Ethernet). Unless you are planning to
be running very high-speed services out of your home, Category 3 wiring,
rated to carry 10 megabit Ethernet service, should be sufficient. Data
wiring should always be wired in a star configuration, and should use shielded,
twisted-pair cable designed to minimize interference and signal loss. Do
not use standard phone wire for Ethernet cabling. Your installer should
also have a 10BaseT test set so that he or she can verify that the cable
is OK, and is capable of carrying Ethernet signals without errors.
The LAN cable runs will, in turn, be connected to an Ethernet hub or
switch which is located near the central wiring point. If you anticipate
having many computers sharing your LAN, with a lot of data traffic, we
recommend using an Ethernet switch. Ethernet switches provide higher effective
speeds than Ethernet hubs, which are cheaper. Ethernet hubs are perfectly
adequate for typical home uses though. You wire your Ethernet cable runs
to the hub or switch, and then you have high-speed data "dialtone" running
throughout your house.