NETWORK CABLE AND CONNECTORS
Last updated: 2/11/2000

There are several classifications of cable used for twisted-pair networks.  I'll skip right over them and state that I use and recommend Category 5 (or CAT 5) cable for all new installations.  Likewise, there are several fire code classifications for the outer insulation of CAT 5 cable.  I use CMR cable, or "riser cable," for most of the wiring I do.  You should also be aware of CMP or plenum cable (a plenum is used to distribute air in a building).  You may be required by local, state or national codes to use the more expensive plenum-jacketed cable if it runs through suspended ceilings, ducts, or other areas, if they are used to circulate air or act as an air passage from one room to another.  If in doubt, use plenum.  CMR cable is generally acceptable for all applications not requiring plenum cable.

CAT 5 wire is available in reel-in-box packaging. This is very handy for pulling the wire without putting twists in it.  Without this kind of package or a cable reel stand, pulling wire is a two-person job.  Before the advent of the reel-in-box, we used to put a reel of wire on a broom handle to pull it.  One person would hold the broom handle and the other would pull and measure the cable.  You will produce a tangled mess, if you pull the wire off the end of the reel.

Stranded wire patch cables are often specified for cable segments running from a wall jack to a PC and for patch panels.  They are more flexible than solid core wire.  However, the rational for using it is that the constant flexing of patch cables may wear-out solid core cable--break it.  I don't think this is a real concern in the average small network.   For example, I have one solid core cable going to my work bench.  It has probably flexed and average person's lifetime of flexes from the many many times I have connected customer computers to my network.   Also, stranded cable is susceptible to degradation from moisture infiltration, may use an alternate color code, and should not be used for cables longer than 3 Meters (about 10 feet).

Most of the wiring I do simply connects computers directly to other computers or hubs.  Solid core cable is quite suitable for this purpose and for many home and small business networks.   I find it also quite acceptable for use as patch cables.  You might consider a stranded wire patch cable if you have a notebook computer you are constantly moving around.

CAT 5 cable has four twisted pairs of  wire for a total of eight individually insulated wires.   Each pair is color coded with one wire having a solid color (blue, orange, green, or brown) twisted around a second wire with a white background and a stripe of the same color.   The solid colors may have a white stripe in some cables.  Cable colors are commonly described using the background color followed by the color of the stripe; e.g., white-orange is a cable with a white background and an orange stripe.

CONNECTORS.   The straight through  and cross-over patch cables discussed in this article are terminated with CAT 5 RJ-45 modular plugs.  RJ-45 plugs are similar to those you'll see on the end of your telephone cable except they have eight versus four or six contacts on the end of the plug and they are about twice as big.  Make sure they are rated for CAT 5 wiring.  (RJ means "Registered Jack").  Also, there are RJ-45 plugs designed for both solid core wire and stranded wire.  Others are designed specifically for one kind of  wire or the other.  Be sure you buy plugs appropriate for the wire you are going to use.  I use plugs designed to accommodate both kinds of wire.

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