Specifications

13
5 Wiring Techniques – The Nuts & Bolts
Many of the advances in termination technology were developed by the Telephone industry to deal with the
massive number of circuits they install and manage. Of particular note for our purposes are Modular jacks
and type 66 and 110 punch down blocks.
Modular jacks were developed by the old Bell System to reduce the cost of installing and maintaining
customer equipment. Until the mid 1970s phone cords were hardwired. This required a craftsperson to
come on site for even the simplest of jobs. The deployment of modular jacks meant that in many cases the
customer could repair and move their own equipment. The six-position version of the modular jack is used
to connect single and two line phones to facility wiring. A smaller four-position version is used at both ends
of the handset cable. TIA568 adopted the 8-position modular connector for use with structured network
wiring.
The jacks are commonly called RJxx for registered jack. This stems from the pre divesture days when each
use of the jack had to be documented in the telephone tariff.
About the same time as modular jacks became popular Type 66 punch down termination was introduced. It
is called punch down because the wire is terminated with a spring-loaded tool that pushes it between
insulation displacement contacts and automatically cuts the wire to length. The type 66 block is still widely
used in phone systems. LAN wiring adopted second generation, type 110, termination. This allows more
circuits to be terminated in a given area. Due to smaller size the 110 contact provides better high frequency
performance.
A significant portion of overall phone system or LAN cost is in the cabling. Until EIA/TIA568 each
equipment vendor created unique cabling and connector requirements. The TIA recognized cable
infrastructure has a long life expectancy, typically being used with multiple generations of electronic
equipment. They developed a performance based wiring scheme independent of the specific equipment
used. This was a breakthrough, all new telephone premise and LAN wiring is based on the standards
developed by TIA568. A companion document EIA570 addresses unique aspects of residential wiring.
When the telephone network was deregulated the FCC took over responsibility for setting customer
equipment and inside wiring standards, commonly called Customer Premise Equipment. Phone company
practice for the last 100 years has been to wire phone jacks as a daisy chain. Wire originates at the NID and
runs to the first outlet, from there to the next, and so on. As customers began using more sophisticated
services the limitation of this method became apparent. The FCC recently mandated telephone inside
wiring be installed using homerun method with at least EIA568 Cat3 twisted pair cable. Homerun wiring
requires each outlet have a separate cable that runs all the way back to a central wiring closet. This provides
a great deal of flexibility for change and reconfiguration.
A useful wiring guide is the “Technician’s Handbook -- Communications Cabling” by James Abruzzino
ISBN 0-9671630-0-5. A free online guide is available from Levitron.
Wiring supplies can be purchase at electrical supply houses or on line from Mike Sandman.
5.1 Structured Wiring
The key to the EIA 568 standard is the notion of structured wiring. Cable from each data or phone outlet is
run back to a central wiring closet. The wire cannot be spliced or connected to other outlets. At the wiring
closet each cable is terminated at a patch panel. To configure a specific service a short cable, called a patch
cable is connected between the appropriate patch panel jack and the device that services that outlet.
EIA/TIA 568 created different performance grades. Category 3, also called Cat3 is rated for 10Mbp/s. This
is the minimum acceptable standard for telephone and digital networks. Cat5e is required for 100Mbp/s
networks, and is the minimum recommended for new LANs. Cat5e allows the LAN to operate at up to
1000BaseT Ethernet. This allows a single wiring scheme to support Ethernet (10Mbp/s), Fast Ethernet