The Commercial Building Telecommunications Cabling Standard, ANSI/TIA/EIA- 568-A, defines categories for 100- unshielded, twisted-pair cables. The Category 3 designation applies to cables and hardware up to 16 MHz (16 Mbs). The Category 4 designation applies to cables and hardware up to 20 MHz (20 Mbs). The Category 5 designation applies to cables and hardware up to 100 MHz (100 Mbs). The Category 5e designation applies to cables and hardware over 100 MHz (over 250 Mbs). The Category 6 designation applies to cables and hardware over 250 MHz (over 500 Mbs). Practically speaking, CAT 3 cable is used for high-pair count outdoor and high-pair count backbone voice cable, and occasionally for station cable (from the closet to the phone). CAT 4 cable is nonexistent, at 20 MHz it is too close to CAT 3 to warrant manufacture. CAT 5 cable is used for low-end data installations and voice cable. CAT 5e, where ‘‘e’’ stands for enhanced, and CAT 6 are not ANSI/TIA/EIA standards at this writing, so it is necessary to look at the cable and system specifications and test results to determine performance. Most new installations should be CAT 5e or CAT 6 for economic reasons. One of the differences between CAT 5e and CAT 6 will be that the patch cable will be required to be CAT 6 and coordinated with the system. Using CAT 5e or CAT 6 for new installations is good for the industry, because currently there are many poor patch cables in use choking the speed of PCs.
Horizontal cabling generally refers to cabling run from the communications closet to the workstation. A link specifically refers to the workstation outlet, the horizontal cabling, and the communications closet patch panel. A channel specifically refers to the cabling from the PC to the communications closet network gear, including all of the patch cables and the patch-panel connectors. Standard channel and link performance warranties are offered by the manufacturers for 15 years.
Where the cable and jacks are made by different manufacturers, the jack manufacturer administers the warranty. It is extremely important to match the two manufacturers.
Warranties are also available from some manufacturers for the entire cabling plant; i.e., for channels, backbone cabling, and campus cabling, including the fiberoptics. One of the problems with not coordinating cable and jack manufacturers happens over time—the connections at the jack become slightly loose and the network speed degrades until re-terminating the entire system becomes the best option. A 15-year warranty is preferred.
It is important to note the economic advantage of using a Category 6 solution.
To implement Gigabit Ethernet on CAT 6, the network electronics will use two pairs of the cable to transmit 500 Mbps and two pairs to receive 500 Mbps. To implement Gigabit Ethernet on CAT 5e requires all four pairs to transmit and receive 250 Mbps. The network gear and the network interface cards (NICs) in the PC are much more expensive for the CAT 5e solution. The only difficulty is that the cabling is usually in the construction budget, and the electronics are in the IT budget.
Installing CAT 5 and better cable requires adherence to a few principles. The installer must not exceed the cable’s minimum-bending radius (crush the cable) or exceed the cable’s tensile strength, and he must properly terminate the cable. The most common office installation is to use CAT 5-rated J-hooks at 5-ft intervals above the drop ceiling. Cable trays may be used. Conduit may be used, but the permissible number of bends must be calculated. A limit of 180 (two 90 bends) between pull boxes is preferred. The installer must not exceed the ratings of the Jhooks, cable tray, conduit, communications poles, and the furniture wire ways. (See Figs. 18.15–18.23.)