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Appendix C
IEEE 802.3 Quick Primer
10BASE-T
10BASE-T UTP media were implemented to reduce Ethernet wiring costs.
UTP wiring is installed in most buildings for telephone systems. Make
sure the UTP wiring used for 10BASE-T is able to carry the high Ethernet
data rates before you implement a 10BASE-T network solution.
Unlike coaxial Ethernet, 10BASE2 and 10BASE5, 10BASE-T UTP is
point-to-point wiring. Typically, one end is connected to an Ethernet
10BASE-T NIC or transceiver (MAU) and the other end is connected to a
10BASE-T hub (repeater). Straight-through cabling pin-out is used for
hub-to-MAU connections. Hub-to-hub and MAU-to-MAU connections are
allowed when you use a UTP cable with a crossover function crossing TD+
and TD- with RD+ and RD- signals. No other attachments are allowed
along the length of the UTP wire; however, wiring patch panels and
punch-down blocks are allowed for interconnecting segments. The cable
should be at least Level 3 UTP, 100
Ω
impedance, 22 to 26 AWG, and
should not exceed 100 meters (328 ft.) in length from one end to the other.
See Table 8 on page 62 for comparison of different UTP cables.
Four-Repeater Rule
Up to four repeater units may be connected, for a total of five segments,
provided that two of the segments are link segments. Link segments (such
as fiber) have no MAU attachments. If all segments are coax segments
with MAU attachments, a maximum of two repeater units and three
segments is allowed.
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