Cisco VG202 Руководство по установке оборудования - Страница 27

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Также для Cisco VG202: Руководство по настройке программного обеспечения (50 страниц), Руководство (10 страниц), Руководство по установке оборудования (48 страниц), Краткое руководство по эксплуатации (19 страниц)

Chapter 2

Planning Your Installation

FXS Analog Voice Port Maximum Distance

The maximum distance is established by a total allowable loop resistance, including the phone or

terminal equipment, of 600 ohm.

When you run cables for any significant distance in an electromagnetic field, interference can occur

between the electromagnetic field and the signals on the cables. This has two implications for the

installation of terminal plant cabling:

•

If you use twisted-pair cables with a good distribution of grounding conductors in your plant cabling,

then emitted radio interference is unlikely.

If your cables exceed the recommended distances, or if your cables pass between buildings, you must

give special consideration to the effect of lightning strikes or ground loops. If your site has these

characteristics, consult experts in lightning suppression and shielding. The electromagnetic pulse caused

by lightning or other high-energy phenomena can easily couple enough energy into unshielded

conductors to destroy electronic devices.

Most data centers cannot resolve the infrequent but potentially catastrophic problems of EMI without

using pulse meters and other special equipment. Take precautions to avoid these problems by providing

a properly grounded and shielded environment and by installing electrical surge suppression.

If you remove any module, you must either install a module in its place or install a cover plate over the

opening. To prevent electromagnetic interference, all module openings must be either occupied or

covered.

For advice on the prevention of electromagnetic interference, consult experts in radio-frequency

interference (RFI).

OL-15959-01

Unshielded plant cabling can emit radio interference.

Strong electromagnetic interference (EMI), especially that caused by lightning or radio transmitters,

can destroy the EIA/TIA-232 drivers and receivers in the Cisco VG202 and Cisco VG204 voice

gateways.

Cisco VG202 and Cisco VG204 Voice Gateways Hardware Installation Guide

Interference Considerations

2-3