CentreCOM 3600 Series Hub/Repeaters
65
If you pair pins incorrectly, for example as shown in Figure 9, Diagram B,
your network may have a high data error rate. In a straight-through cable,
the transmit pins, 1 and 2, are paired, as are the receive pins, 3 and 6. In a
crossover cable (Figure 8), pins 1 and 2, TD+ and TD-, are paired, as are pins
3 and 6, RD+ and RD-. When pins 1 and 2 are crossed over, they connect to
pins 3 and 6 respectively, and pins 3 and 6, when crossed over, connect to pins
1 and 2 respectively.
10BASE-FL/FOIRL Ethernet
The IEEE 802.3 10BASE-FL standard supports up to 2,000 meters (6,560 ft.)
of multimode duplex fiber optic cable in a point-to-point link which directly
attaches two devices. Duplex refers to support for fiber optic cable pairs,
enabling a two-cable fiber optic connection with transmit mode dedicated to
one cable and receive mode on the other. 10BASE-FL supports connections of
2,000 meters (6,560 ft.) while FOIRL supports connections of 1,000 meters
(3,280 ft.). FL is compatible with FOIRL, but restricts distance to 1,000
meters (3,280 ft.).
10BASE5 (Thick) Ethernet
When configuring 10BASE5 coax segments, 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 cannot 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 typically connects a transceiver attached to a coaxial segment to a DTE
(workstation).
10BASE2 (Thin) Ethernet
When configuring thin coax segments, IEEE 802.3 specifications allow 29 or
fewer MAUs per cable segment spaced at no less than 0.5 meter (1.64 ft.). The
10BASE2 cable length cannot exceed 185 meters (607 ft.) per 10BASE2 cable
segment. The worst case propagation delay for a 185 meters (607 ft.) thin
Ethernet segment is 950.9 ns. The propagation delay for 10BASE2 Ethernet
cable is 5.14 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.
