Twisted-pair cable consists of two insulated copper wires twisted together in a helical pattern. Its key transmission characteristics are:

1. Signal type — carries analog or digital electrical signals.

2. Bandwidth — limited compared to coaxial or fiber; UTP Cat 5e/6 supports up to a few hundred MHz to ~500 MHz of usable bandwidth, enough for 1–10 Gbps over short distances.

3. Attenuation — signal strength decreases with distance and increases with frequency; requires repeaters/amplifiers over long runs (typically limited to ~100 m for Ethernet UTP before needing a repeater).

4. Noise susceptibility — vulnerable to electromagnetic interference (EMI) and crosstalk from adjacent pairs/cables, since the copper conductors are exposed to external fields. Twisting reduces (but doesn't eliminate) this by promoting equal noise pickup on both wires, which cancels out under differential signaling.

5. Two variants:

   • UTP (Unshielded Twisted Pair) — no extra shielding, cheaper, more prone to interference.
   • STP (Shielded Twisted Pair) — has metallic foil/braid shielding around the pairs, better noise immunity, but more expensive and harder to install.

6. Cost and ease of installation — the cheapest and easiest guided medium to install and terminate, which is why it dominates LAN cabling despite its bandwidth/distance limitations relative to fiber.