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Smart Switch Series Software Manual
D-6 Cabling Guidelines
July 2005
Unlike 10BASE-T and 100BASE-TX, which use only two of the four pairs of wires within the
Category 5, 1000BASE-T uses all four pairs of the twisted pair. Make sure all wires are tested ⎯
this is important.
Factors that affect the return loss are:
The number of transition points, as there is a connection via an RJ-45 to another connector, a patch
panel, or device at each transition point.
Removing the jacket that surrounds the four pairs of twisted cable. It is highly recommended that,
when RJ-45 connections are made, this is minimized to 1-1/4 inch (32 mm).
Untwisting any pair of the twisted-pair cabling. It is important that any untwisting be minimized to
3/8 inch (10 mm) for RJ-45 connections.
Cabling or bundling of multiple Category 5 cables. This is regulated by ANSI/EIA/TIA-568A-3. If
not correctly implemented, this can adversely affect all cabling parameters.
Near End Cross Talk (NEXT)
This is a measure of the signal coupling from one wire to another, within a cable assembly, or
among cables within a bundle. NEXT measures the amount of cross-talk disturbance energy that is
detected at the near end of the link — the end where the transmitter is located. NEXT measures the
amount of energy that is “returned” to the sender end. The factors that affect NEXT and cross talk
are exactly the same as outlined in the Return Loss section. The cross-talk performance is directly
related to the quality of the cable installation.
Patch Cables
When installing your equipment, replace old patch panel cables that do not meet Category 5e
specifications. As pointed out in the NEXT section, this near end piece of cable is critical for
successful operation.
RJ-45 Plug and RJ-45 Connectors
In a Fast Ethernet network, it is important that all 100BASE-T certified Category 5 cabling use
RJ-45 plugs. The RJ-45 plug accepts 4-pair UTP or shielded twisted-pair (STP) 100-ohm cable
and connects into the RJ-45 connector. The RJ-45 connector is used to connect stations, hubs, and
switches through UTP cable; it supports 10 Mbps, 100 Mbps, or 1000 Mbps data transmission.