Cabletron Systems 100BASE-FX, Cabling Manual

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Token Ring Network Requirements
10-6 IEEE 802.5 Unshielded Twisted Pair
Impedance
All UTP cabling used in a Token Ring installation must test to an impedance of 85
to 115 Ohms. Cabling with higher or lower impedance ratings may not operate
properly in the Token Ring network environment.
Crosstalk
Crosstalk is electrical interference between wires. Crosstalk occurs when a cable
strand absorbs signals from other wires that it is adjacent to. Excessive crosstalk
can be caused by a break in the insulation or shielding that separates wires from
one another in a bundle.
Token Ring UTP cables should be checked for Near-End Crosstalk, or NEXT, at
installation.
Category 3
The maximum acceptable amount of near-end crosstalk for a Category 3 UTP link
is 23 dB/1000 ft.
Category 4
The maximum acceptable amount of near-end crosstalk for a Category 4 UTP link
is 36 dB/1000 ft.
Category 5
The maximum acceptable amount of near-end crosstalk for a Category 5 UTP link
is 44 dB/1000 ft.
Link Length
Category 3, 4
UTP cabling of Categories 3 and 4 are similar enough in quality to receive similar
treatments and specifications under the IEEE 802.5 standard. Cabling of Category
3 or 4 is allowed different maximum link lengths based on the speed of the
network and the use of active or passive Token Ring circuitry.
In an active network, a UTP link using Category 3 or 4 UTP may be 200 m (656 ft)
or less at 4 Mbps. A 16 Mbps active Token Ring network may support a Category
3 or 4 link of up to 100 m (328 ft).