Safety; Preparing For Installation - Cisco uBR-3x10 Hardware Installation And Cabling Manual

Chapter 2

Preparing for Installation

Provisioning the Headend
The following sections describe the provisioning required at the cable headend before you install the
Cisco uBR 3x10 RF Switch.
Headend Certification
The cable headend plant must pass both analog and digital certification:
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Headend Wiring
This section provides guidelines for setting up the headend wiring and cabling at your site. When
planning the location of the new system, consider the distance limitations for signaling, electromagnetic
interference (EMI), and connector compatibility, as described in the following sections:
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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
headend wiring:
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If you use twisted-pair cable in your headend wiring with a good distribution of grounding conductors,
the wiring is unlikely to emit radio interference. If you exceed the recommended distances, use a
high-quality twisted-pair cable with one ground conductor for each data signal when applicable.
If wires exceed 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 EMI problems in the past, you might want to consult experts in
electrical surge suppression and shielding.
Distance Limitations and Interface Specifications
The size of your networks and the distances between connections depend on the type of signal, the signal
speed, and the transmission media (the type of cabling used to transmit the signals). For example,
standard coaxial cable has a greater channel capacity than twisted-pair cabling. The distance and rate
limits in the following descriptions are the IEEE recommended maximum speeds and distances for
OL-1984-06
In the United States, the Federal Communications Commission (FCC) mandates certification.
For international certification, consult with local agencies for certification requirements.
Interference Considerations
Distance Limitations and Interface Specifications
Bad wiring practice can result in radio interference emanating from the wiring, ingress noise,
co-channel interference, and degraded or erratic universal broadband router performance.
Strong EMI, especially when caused by lightning or radio transmitters, can destroy the signal drivers
and receivers in the Cisco RF switch, and can even create an electrical hazard by conducting power
surges through lines and into equipment. (Review the safety warnings in the
Electricity" section on page 2-3.)
Cisco uBR-3x10 RF Switch Hardware Installation and Cabling Guide
Provisioning the Headend
"Safety with
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