Network Card User Manual
Preparing for Installation 2-13
Plant Wiring
Plant Wiring
The following are guidelines for setting up the plant wiring and cabling at your site. When planning
the location of the new system, consider the distance limitations for signaling, EMI, and connector
compatibility, as described in the following sections.
Interference Considerations
When wires are run for any significant distance in an electromagnetic field, interference can occur.
This fact has two implications for the construction of plant wiring:
• Bad wiring practice can result in radio interference emanating from the plant wiring.
• Strong EMI, especially when caused by lightning or radio transmitters, can destroy signal drivers
and receivers and can even create an electrical hazard by conducting power surges through lines
and into equipment. (Review the safety warnings in the section “Maintaining Safety with
Electricity,” earlier in this chapter.)
Note To predict and remedy strong EMI, you might need to consult experts in radio frequency
interference (RFI).
If you use twisted-pair cable in your plant wiring with a good distribution of grounding conductors,
the plant 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 such problems have occurred in the past, you may want
to consult experts in electrical surge suppression and shielding.
Distance Limitations and Interface Specifications
The size of your network and the distances between connections depend on signal type and speed
and on transmission media (the type of cabling used to transmit the signals). For example, standard
coaxial cable has a greater channel capacity than twisted-pair cable. The distance and rate limits in
the following descriptions are the IEEE recommended maximum speeds and distances for signaling;
however, you can usually get good results at speeds and distances far greater than these. For example,
the recommended maximum rate for V.35 is 2 Mbps, but it is commonly used at 4 Mbps without any
problems. If you understand the electrical problems that might arise and can compensate for them,
you should get good results with rates and distances greater than those shown here; however, do so
at your own risk.
Note We recommend that you do not exceed specified transmission rate and distance limits.