Station Cable

Twisted Pair Wiring Overview
Unshielded twisted pair (UTP) cable is today's norm for inside-building station wiring communications connectivity. This is the phone wire found behind the telephone/data jacks on the walls of offices, classrooms and conference rooms throughout campus. Much of the existing wiring is of the older, 6 pair variety that, although installed originally for telephone circuitry, with some jack modification, does allow LAN connectivity. This older wiring, however, has a relatively high signal to noise ratio, and will not support 100Mbs technology. For this reason, new construction standards dictate the installation of newer, Category 5 type twisted pair inside wire.

Because Ethernet is the protocol of choice for most LAN's at U of M, using twisted pair to access a network limits the length of station wire feeding a jack to about 100 meters (330 feet). Distances exceeding 100 meters do not operate reliably. The wiring of new buildings, and rewiring of existing buildings for communications is done in a "star topology", that is, each station cable runs back to a communications closet, forming a sort of "star" configuration. Each branch of the star must be limited to 100 meters, including the patch cable plugged into the desktop machine. The communications closets, or LDF's (Local Distribution Frames), are themselves connected to other LDF's, via fiber optics for data communications, and copper wire for telephones, providing an inter campus link.

New Construction and Renovations
Today's standard for wiring on campus is 12 pair of Category 5 UTP cable, 4 pair of which is dedicated for voice circuits, i.e. phones and modems, and the remaining 8 pair for 2 Category 5 data connections. This arrangement will give the customer a jack with 4 inputs: a 2 port voice jack, with a 2 port Ethernet jack directly below it. It is common practice, after installing this configuration, for the technician to run a Category 5 test to ensure that the wiring and related data terminations have been installed properly and will provide at least 100Mbs potential. A hard copy of these test results are then given to the customer for his/her records.

Customized Jack Scenarios
Some customers may foresee the need for more than 2 Category 5 connections at a jack, in which case ITCom can customize the installation per the customer's needs. We have, in some cases, installed scenarios that provide the potential for 2 voice and 3 Category 5 , or on occasion, 4 Category 5 Ethernet connections. Sometimes a computer lab area or training facility will dictate that new jacks have data-only capability when no voice connections are needed.

Cost Conscious Measures
There are times when 100Mbs Ethernet is not a concern, such as when 10Mbs Ethernet is being used and the customer wants to maximize the number of circuits for the money. In this case an 8 pair cable will supply a maximum of 2 voice and 2 data connections. This sort of installation is cheaper because less cable is pulled and labor time is reduced. Sometimes this approach is used as a stop-gap measure when more connections are needed, but a network overhaul is put off because an impending building renovation or department move is on the horizon.

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