Communications and Data Cable (Cat 5e, 6, 6A)

What it is

Category cable carries Ethernet, PoE and other low-voltage signals over four twisted pairs. TIA-568 sets the performance for each category. The fire listing printed on the jacket (CMP, CMR and others) comes from UL 444 testing and the NEC communications articles and tells where the cable may be installed.

How to identify

Read the jacket print: category, conductor size (often 23 or 24 AWG), listing such as CMR or CMP, shielding (U/UTP, F/UTP, S/FTP), the maker and a footage mark. Cat 6 and 6A often have a plastic spline (cross filler) between the pairs. Shielded cable has a foil and a drain wire.

Category and listing comparison

Key points

• The 100 m channel is 90 m of permanent link plus up to 10 m of patch cords.
• Use connectors, jacks and patch panels rated for the same category. One lower-rated part lowers the whole link.
• Shielded cable must be bonded through shielded jacks and panels to work. An unbonded shield can make noise worse.
• PoE heats cable bundles. Larger bundles and higher PoE power may need derating per the cable maker and the NEC.
• Solid conductors are for horizontal runs. Stranded cable is for patch cords.
• Recent NEC editions moved communications cable rules into Articles 800 and 805. Check the edition in force.

Common mistakes

• Running CMR cable in a plenum ceiling.
• Untwisting pairs too far back at a termination.
• Using stranded patch cable for long horizontal runs.
• Mixing Cat 5e jacks with Cat 6A cable and expecting 6A results.

Governing standards: TIA-568 (cabling performance); UL 444 (communications cable); NEC Article 800 series (communications circuits).

Reference only. Verify against the current governing code or standard, the manufacturer's data and the project documents before use. Apps for Distributors disclaims liability arising from reliance on this reference.