Twisted Pair Cable Categories

Despite all the talk of fiber and Wi-Fi, twisted-pair copper cable still carries most local network traffic. It is cheap, flexible, and easy to install. Twisted pair is built from pairs of copper wires twisted together inside a jacket. Different categories (often shortened to "Cat") support different speeds and distances. Knowing the categories lets you pick the right cable for a job — a core skill the Network+ exam tests.

The twisting is not decoration — it fights interference. When two wires carry a signal and are twisted together, outside electrical noise hits both wires almost equally and cancels out. This is called rejecting EMI (Electromagnetic Interference) and reducing crosstalk (signal bleeding between pairs). Tighter, more consistent twists allow higher speeds, which is part of why higher categories perform better.