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Cisco ASR 903 Router Hardware Installation Guide
OL-25178-04
Chapter 2 Preparing for Installation
Site Planning
The extent of your network and the distances between the network interface connections depend in part
on the following factors:
• Signal type
• Signal speed
• Transmission medium
The distance and rate limits referenced in the following sections are the IEEE-recommended maximum
speeds and distances for signaling purposes. Use this information as a guideline in planning your
network connections prior to installing the Cisco ASR 903 Router.
If wires exceed the recommended distances, or if wires pass between buildings, give special
consideration to the effect of a lightning strike in your vicinity. The electromagnetic pulse caused by
lightning or other high-energy phenomena can easily couple enough energy into unshielded conductors
to destroy electronic devices. If you have had problems of this sort in the past, you may want to consult
experts in electrical surge suppression and shielding.
Asynchronous Terminal Connections
The RSP provides a console port to connect a terminal or computer for local console access. The port
has an RJ45 connector and supports RS-232 asynchronous data with distance recommendations
specified in the IEEE RS-232 standard.
Interference Considerations
When wires are run for any significant distance, there is a risk that stray signals will be induced on the
wires as interference. If interference signals are strong, they can cause data errors or damage to the
equipment.
The following sections describe sources of interference and how to minimize its effects on the
Cisco ASR 903 Router system.
Electromagnetic Interference
All equipment powered by AC current can propagate electrical energy that can cause EMI and possibly
affect the operation of other equipment. The typical sources of EMI are equipment power cords and
power service cables from electric utility companies.
Strong EMI can destroy the signal drivers and receivers in the Cisco ASR 903 Router and even create an
electrical hazard by causing power surges through the power lines into installed equipment. These
problems are rare but could be catastrophic.
To resolve these problems, you need specialized knowledge and equipment that could consume
substantial time and money. However, you can ensure that you have a properly grounded and shielded
electrical environment, paying special attention to the need for electrical surge suppression.
For information about the electrode magnetic compliance standards supported on the
Cisco ASR 903 Router, see Regulatory Compliance and Safety Information for the
Cisco ASR 903 Router.
Radio Frequency Interference
When electromagnetic fields act over a long distance, radio frequency interference (RFI) may be
propagated. Building wiring can often act as an antenna, receiving the RFI signals and creating more
EMI on the wiring.