31
R
ECOMMENDATIONS
FOR
C
ABLES
IN
H
IGH
E
LECTRICAL
N
OISE
C
HAPTER
9
D
EVICE
M
ANAGEMENT
1000 Base-T MDI/MDI- X pin assignments are as follows:
1000 Base-T RJ-45 pin assignments are as follows:
NOTE
:
“+” and “-” signs represent the polarity of the wires that make each wire pair.
9.4. Recommendations for Cables in High Electrical Noise
Constant electrical noise can be due to the predictable 50 or 60 Hz AC 'hum' from power circuits or
harmonic multiples of power frequency close to the data communications cable.
Follow these recommendations for copper data cabling in high electrical noise environments:
•
Data cable lengths should be as short as possible, preferably 3 m (10 ft) in length. Copper data
cables should not be used for inter-building communications.
PIN #
MDI PORT
MDI-X PORT
1
TD+ (transmit)
RD+ (receive)
2
TD- (transmit)
RD- (receive)
3
RD+ (receive)
TD+ (transmit)
4
Not used
Not used
5
Not used
Not used
6
RD-(receive)
TD-(transmit)
7
Not used
Not used
8
Not used
Not used
PIN #
MDI PORT
MDI-X PORT
1
BI_DA+
BI_DB+
2
BI_DA-
BI_DB-
3
BI_DB+
BI_DA+
4
BI_DC+
BI_DD+
5
BI_DC-
BI_DD-
6
BI_DB-
BI_DA-
7
BI_DD+
BI_DC+
8
BI_DD-
BI_DC-
