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7000 Series L3 Managed Switch Reference Manual for Software v2.0
Cabling Guidelines A-3
Table 10-1. Electrical Requirements of Category 5 Cable
Twisted Pair Cables
For two devices to communicate, the transmitter of each device must be connected to the receiver
of the other device. The crossover function is usually implemented internally as part of the
circuitry in the device. Computers and workstation adapter cards are usually media-dependent
interface ports, called MDI or uplink ports. Most repeaters and switch ports are configured as
media-dependent interfaces with built-in crossover ports, called MDI-X or normal ports. Auto
Uplink technology automatically senses which connection, MDI or MDI-X, is needed and makes
the right connection.
Figure A-1 illustrates straight-through twisted pair cable.
Figure A-1: Straight-Through Twisted-Pair Cable
SPECIFICATIONS CATEGORY 5 CABLE REQUIREMENTS
Number of pairs Four
Impedance 100 ± 15%
Mutual capacitance at 1 KHz 5.6 nF per 100 m
Maximum attenuation
(dB per 100 m, at 20° C)
at 4 MHz: 8.2
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