40
Connecting an Ethernet cable
Overview
10/100 Mbps Ethernet uses category-5 twisted pair cables, while 1000 Mbps Ethernet uses
category-5 enhanced or category-6 twisted pair cables. Twisted pair cables include straight-through
cables and crossover cables.
Category-5 cables provide a transmission frequency of 100 MHz for voice and data transmission;
they are mainly used in 100Base-T and 10Base-T networks. Category-5 cables are common
Ethernet cables, which can also be used to transmit 1000 Mbps Ethernet data.
Category-5 enhanced cables feature low attenuation and crosstalk, providing higher attenuation to
crosstalk ratio (ACR), less delay error and higher performance than category-5 cables. Category-5
enhanced cables are mainly used in 1000 Mbps Ethernet networks.
Category-6 cables provide a transmission frequency of 1 MHz to 250 MHz, and improve the
performance on crosstalk and return loss. A fine better return loss performance is extremely
important for new-generation full-duplex high-speed networks. Category-6 cables have sufficient
power sum ACR (PS-ACR) when working at 200 MHz. They provide a bandwidth two times than that
of category-5 enhanced cables, thus featuring a higher transmission performance. Therefore,
category-6 cables are suitable for applications requiring a transmission speed of more than 1 Gbps.
The 10/100 Mbps Ethernet uses two pairs of cables, orange/white, orange, green/white and green
cables, to transmit and receive data, while the 1000 Mbps Ethernet uses four pairs of cables to
transmit and receive data.
An Ethernet twisted pair cable connects network devices through the RJ-45 connectors at the two
ends.
shows the pinouts of an RJ-45 connector.
Figure 41 RJ-45 connector pinout
EIA/TIA cabling specifications define two standards, 568A and 568B, for cable pinouts.
•
Standard
568A
—Pin 1: white/green stripe, pin 2: green steady, pin 3: white/orange stripe, pin 4:
blue steady, pin 5: white/blue stripe, pin 6: orange steady, pin 7: white/brown stripe, pin 8: brown
steady.
•
Standard
568B
—Pin 1: white/orange stripe, pin 2: orange steady, pin 3: white/green stripe, pin
4: blue steady, pin 5: white/blue stripe, pin 6: green steady, pin 7: white/brown stripe, pin 8:
brown steady.
Ethernet twisted pair cables can be classified into straight-through and crossover cables based on
their pinouts
For the pinouts of the twisted pair cables, see the following tables. (A and B represent the two ends of
a cable, respectively.)
PIN #8
PIN #1
