Cisco Explorer 4700, Hardware Installation And Maintenance Manual

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2-18 Cisco 4000 Series Hardware Installation and Maintenance
Network Connection Considerations
Interference Considerations
When wires are run for any significant distance in an electromagnetic field, interference can occur
between the field and the signals on the wires. This fact has two implications for the construction of
terminal plant wiring:
•
Plant cabling can emit radio frequency interference (RFI) if it is unshielded for a distance
exceeding those recommended by the standard.
•
Strong electromagnetic interference, especially as caused by lightning or radio transmitters, can
destroy the EIA/TIA-232 drivers and receivers in a router.
If you use twisted-pair cables in your plant wiring with a good distribution of grounding conductors,
the plant wiring is unlikely to emit radio interference. Ground the conductor for each data signal
when exceeding the distances listed in Table 2-4.
If you have cables exceeding the distances in Table 2-4, or if you have cables that pass between
buildings, then give special consideration to the effect of lightning strikes and ground loops. The
electromagnetic pulse caused by lightning and other high-energy phenomena can couple enough
energy into unshielded conductors to destroy electronic devices; the potential existence of ground
loops are also a threat to electrical components and to safety. If your site has experienced these
problems, then consult experts in lightning suppression and shielding.
Most data centers cannot resolve the infrequent but potentially catastrophic problems just described
without pulse meters and other special equipment. Take precautions to avoid these problems by
providing a properly grounded and shielded environment, with special attention to issues of
electrical surge suppression. To predict and remedy strong electromagnetic interference, consult
experts in RFI.
Configuring Serial Connections
The four-port serial network processor module ports are DB-60 connectors; the dual serial network
processor module ports are DB-50 connectors. (See Figure 2-18 and Figure 2-20.) These serial ports
can be configured as DTE or DCE, depending on the special serial cable used.
Figure 2-18 shows port numbering on the four-port serial module.
Figure 2-18 Four-Port Serial Network Processor Module Ports
60-Pin
ports
H1981
PORT-3 PORT-2
PORT-1 PORT-0
P-3
P-1
P-2
P-0
P-3 P-2 P-1`
P-0
LP CN TD TC RD RC LP CN TD TC RD RC LP CN TD TC RD RC LP CN TD TC RD RC
LEDs
60-Pin
ports