No matter which design is used you must not exceed 90m(295ft) for the permanent horizontal link cable even if it is fiber. It is always a good practice to keep your patch cords as short as possible to reduce attenuation, reflections and crosstalk. If the horizontal cable used is fiber then the methodology of making connections changes slightly. When using a fiber link we do not use interconnects. The fiber equipment is directly patched to the horizontal fiber link. Fiber cable is terminated with male connectors which are aligned together in a device called an adaptor. An adaptor is simply a hollow cylindrical device that aligns the two male fiber connectors. The variation allowed for connecting our horizontal cable to a connector is this. We may either directly connect or use a pigtail with a fusion or mechanical splice or we may use mechanical splice connectors. This connection may be specified but if not I would choose a pigtail for single mode (fusion splice) or direct connectorisation for multimode as they are fast to fit off and less expensive.

Channel and Permanent Link
It is important to note this terminology as it is applied when testing our cable elements. The permanent link is the physical horizontal cable element without any patching. A channel is measured from equipment to equipment or from HUB to NIC which includes all patching that is used, Interconnect, crossconnect and work area patching. A Channel test will verify the complete circuit but a permanent link test only tests the horizontal cable element. On the whole a cabler will only test the permanent link.

Choosing Cable Types
The standards allow designers two alternatives when choosing UTP or fiber cable types. The preferred choice is :

• 100W balanced UTP cable
• 62.5m/125mm multimode optical fiber cable

The alternative cable choice is :

• 120W balanced UTP cable
• 150W balanced UTP cable
• 50m/125mm multimode fiber optic cable
• 9m/125mm single mode fiber optic cable

Shielding of copper cable is another option but it is generally not needed and not preferred as it introduces greater losses and thus all dimensions discussed here would be significantly reduced. The performance standards recommended for copper cable styles are referred to as Category 5, Category 5 enhanced and Category 6. For a new installation the minimum Category should be Cat5e or preferably Cat6. The Category of the cable is a reference to the cables ability to carry data which is related to the frequency components of that data signal. Thus cables are also referenced by a "Class" which indicates the upper frequency level of a cable. Cat 5 and Cat5e are referenced to Class D which has an upper limit of 100MHz. Cat 6 cable has a Class E reference which has an upper limit of 250MHz. Cat 6 has more than double the bandwidth of Cat 5 cables. Different manufacturers will produce cables that go beyond these classifications. That's fine but once again if you use a 350MHz rated cable then make sure you use 350MHz rated plugs, sockets and patch cords. Once again I must state the obvious. Matching your components to your cable is critical.

Telecommunications Outlets
When configuring TO's at the work area the standards again give you some choices in your design. Your choices are listed below but no matter what you choose there is to be 2 TO's for each work station or each work area.

• One TO is to be a socket capable of terminating a 4 pair UTP cable, minimum Cat 5 100W balanced cable
• The second TO shall be the same as the first TO or it may be fiber, SC fittings preferred