Data Cabling Techniques
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10BASE5 (Thick) Ethernet
For 10BASE5 coax segment configurations, IEEE 802.3 specifications
allow 100 MAU attachments or less, spaced at multiples of 2.5 meters
(8.2 ft.) measured accurately from the cable end (50
Ω
terminator
included). The 10BASE5 cable segment can not exceed 500 meters
(1,640 ft.) in length. Worst case “end-to-end” propagation delay of a
10BASE5 coax segment is 2165 ns. Propagation delay of 10BASE5
Ethernet coax is calculated at 4.33 ns/meter. Both ends of the segment
must be terminated with a 50
Ω
termination with a power rating of
0.5 watts or greater. Earth grounding of the segment shield must take
place at only one point on the cable.
AUI Drop Cables
AUI or Drop cables can be no longer than 50 meters (164 ft.) each.
Attachments may be made only to the cable ends at the 15-pin D-shell
connector. AUI cables may have a maximum 257 ns propagation delay, as
used for computing the worst case propagation delay of a cable system.
AUI cable propagation delay is approximately 5.13 ns/meter. This cable
internally consists of four shielded twisted pair wires with an overall
shield and drain wire; a 15-pin D-shell male connector at one end and a
15-pin D-shell female connector at the other end. Cable impedance is
nominally 78
Ω
. The AUI cable connects a transceiver attached to a coaxial
segment to a DTE (workstation).
