Cisco 10720 Configuration Guide - Page 46

Environmental Safety Guidelines Chapter 2 Preparing for Installation The following guidelines will help to ensure safety and protect the equipment. This list does not include every potentially hazardous situation, so be alert. A Cisco 10720 Internet Router configured with the dual DC-input power supply should have a readily accessible disconnect device incorporated for fixed wiring. See the "Safety Guidelines" section on page 2-2 for additional information. Caution For safety, periodically check the resistance value of the antistatic strap. The measurement should be between 1 and 10 megohms (Mohms). Warning A readily accessible two-pole disconnect device must be incorporated in the fixed wiring. Statement 91 Site Wiring Distance and Interference Guidelines This section offers site wiring guidelines for setting up the site plant wiring and cabling. When planning the location of the new system, consider the following: • Electromagnetic Interference, page 2-10 • Distance Limitations for Signaling and Unshielded Conductors, page 2-10 Electromagnetic Interference Electromagnetic interference (EMI) can occur between the field and the signals on the wires when the wires are run for any significant distance. This fact has two implications for the construction of plant wiring: • Poor wiring practice can result in radio interference emanating from the plant wiring. • Strong EMI, especially when it is caused by lightning or radio transmitters, can destroy and/or cause interference with the signal drivers and receivers in the router, and can create an electrical hazard by conducting power surges through lines and into equipment. Note To predict and remedy strong EMI, consult experts in radio frequency interference (RFI). A good quality twisted pair cable or shielded twisted pair cable helps limit radiation and noise induced into the cable, minimizing the potential for the following: • Radio interference • Interference with the data transmission Distance Limitations for Signaling and Unshielded Conductors You must give special consideration to the effect of a lightning strike in the site vicinity if wires exceed recommended distances, or if wires pass between buildings. The electromagnetic pulse (EMP) caused by lightning or other high-energy phenomena can easily couple enough energy into unshielded conductors to destroy electronic devices. 2-10 Cisco 10720 Internet Router Installation and Configuration Guide 78-13062-10