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www.netcomm.com.au Rev.1 - YML623
Page 14 16-port 10/100Mbps Fast Ethernet ProSwitch
CABLING GUIDELINES
Fast Ethernet Cable Guidelines
Fast Ethernet uses UTP cable, as specified in the IEEE 802.3u standard for 100BASE-TX. The
specification requires Category 5 UTP cable consisting of either 2-pair or 4-pair twisted
insulated copper conductors bound in a single plastic sheath. Category 5 cable is certified up to
100 MHz bandwidth. 100BASE-TX operation uses one pair of wires for transmission and the
other pair for receiving and for collision detection.
When installing Category 5 UTP cabling, use the following guidelines to ensure that your cables
perform to the following specifications:
• Certification
Make sure that your Category 5 UTP cable has completed the Underwriters Laboratories
(UL) or Electronic Testing Laboratories (ETL) certification process.
• Termination method
To minimize crosstalk noise, maintain the twist ratio of the cable up to the point of
termination; untwist at any RJ-45 plug or patch panel should not exceed 0.5 inch (1.5 cm).
Cable Lengths
Category 5 distributed cable that meets ANSI/EIA/TIA-568-A building wiring standards can be
a maximum of 328 feet (100 meters) in length, divided as follows:
• 20 feet (6 meters) between the hub and the patch panel (if used)
• 295 feet (90 meters) from the wiring closet to the wall outlet
• 10 feet (3 meters) from the wall outlet to the desktop device
The patch panel and other connecting hardware must meet the requirements for 100 Mbps
operation (Category 5). Only 0.5 inch (1.5 cm) of untwist in the wire pair is allowed at any
termination point.
Cable Specifications
The following lists he electrical requirements of Category 5 cable.
Specification Category 5 Cable
Number of pairs Four
Impedance 100 & ± 15%
Mutual capacitance at 1 KHz £ 5.6 nF per 100 m
Maximum attenuation at 4 MHz: 8.2
(dB per 100 m, at 20° C) at 31 MHz: 11.7
at 100 MHz: 22.0
NEXT loss (dB minimum) at 16 MHz: 44
at 31 MHz: 39
at 100 MHz: 32