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Ethernet twisted pair cable
Introduction
An Ethernet twisted pair cable consists of four pairs of insulated copper wires twisted together. Every
wire uses a different color, and has a diameter of about 1 mm (0.04 in). A pair of twisted copper
cables can cancel the electromagnetic radiation of each other, and reduce interference of external
sources. An Ethernet twisted pair cable mainly transmits analog signals and is advantageous in
transmitting data over shorter distances. It is the commonly used transmission media of the Ethernet.
The maximum transmission distance of the Ethernet twisted pair cable is 100 m (328.08 ft). To
extend the transmission distance, you can connect two twisted pair cable segments with a repeater.
At most four repeaters can be added, which means five segments can be joined together to provide
a transmission distance of 500 m (1640.42 ft).
Ethernet twisted pair cables can be classified into category 3, category 4, category 5, category 5e,
category 6, and category 7 cables based on performance. In LANs, category 5, category 5e, and
category 6 are commonly used.
Table9-2 Description for commonly used Ethernet twisted pair cables
Type
Category 5
Category 5e
Category 6
Based on whether a metal shielding is used, Ethernet twisted pair cables can be classified into
shielded twisted pair (STP) and unshielded twisted pair (UTP). An STP cable provides a metallic
braid between the twisted pairs and the outer jacket. This metallic braid helps reduce radiation,
prevent information from being listened, and eliminate external electromagnetic interference (EMI) of
external sources. STPs have strict application requirements and are expensive although they
provide better EMI prevention performance than UTPs, so in most LANs, UTPs are commonly used.
An Ethernet twisted pair cable connects network devices through the RJ-45 connectors at the two
ends.
Figure9-2
Figure9-2 RJ-45 connector pinout
PIN #8
PIN #1
NOTE:
The RJ-45 Ethernet ports of the firewall use category 5 or higher Ethernet twisted pair cables for
connection.
EIA/TIA cabling specifications define two standards, 568A and 568B, for cable pinouts.
Description
Suitable for data transmission at a maximum speed of 100 Mbps
Suitable for data transmission at a maximum speed of 1000 Mbps
Suitable for data transmission at a speed higher than 1 Gbps
shows the pinouts of an RJ-45 connector.
9-18
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