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RJ-45 Pin Assignments
Caution: Regulations regarding the connection of equipment
to telephone networks vary from country to country.
Check with your local telephone network supplier
before using existing telephone wiring.
An Ethernet twisted-pair link segment requires two pairs of
wires—Category 3, 4 or 5 for 10 Mbps connections and
Category 5 for 100 Mbps connections. Each wire pair is identi-
fied by two different colors. For example, one wire might be
brown and the other, brown with white stripes.
Caution: Each wire pair must be attached to the RJ-45 connec-
tors in a specific orientation. (See “Twisted-Pair
Cabling Guidelines” in Chapter 3 for an explanation.)
Each twisted-pair link
segment must have an RJ-45
connector attached to both
ends. According to the IEEE
specifications, pins 1 and 2
are used for transmitting
data, and pins 3 and 6 for
receiving data.
*The “+” and “-” signs are used to
represent the polarity of the wires that make up each wire pair.
Note how the
pins are num-
bered. Be sure
to hold the con-
nectors in the
same orientation
when attaching
the wires to the
pins.
PIN ASSIGNMENTS
B-2
Figure B-1. RJ-45 Connector Pin Numbers
Pin Number Assignment*
1 Tx+
2 Tx-
3 Rx+
6 Rx-
RJ-45 Pin Assignments