Transmission Media

Kite Studio is refitting its floor. The electrician asks three questions: what cable goes to the desks, what joins the rack to the building's basement where the fibre arrives, and does the meeting room need cables at all? Every bit on a network rides on some physical medium, and each medium trades speed, distance, cost and convenience differently.

The rule

Copper for desks, glass for distance, radio for freedom.

Media come in two families.

Guided (wired) media keep the signal inside a cable:

• Twisted-pair copper — the everyday Ethernet cable with an RJ45 plug. The wire pairs are twisted to cancel interference. Common grades: Cat5e carries 1 Gbps, Cat6a carries 10 Gbps, and both are rated for runs up to 100 metres. Cheap, easy to terminate, ideal for desks.
• Coaxial — a central copper core inside a shield. Still used for cable-TV internet connections into buildings, rarely inside offices now.
• Fibre optic — pulses of light in thin glass. It carries very high speeds over long distances and is immune to electrical interference. Multimode fibre is cheaper and suited to runs of up to a few hundred metres inside buildings; single-mode fibre reaches many kilometres and links buildings, cities and continents.

Unguided (wireless) media send the signal through the air:

• Radio — Wi-Fi in the 2.4, 5 and 6 GHz bands, plus Bluetooth and mobile networks. No cables and full mobility, but the air is shared, walls weaken the signal and nearby networks interfere.
• Microwave and satellite — point-to-point dishes between towers or rooftops, and links through satellites for remote sites. Satellites far above the earth add noticeable latency simply because of the distance.

The shortcut

For any link, ask three questions in order: How far? How noisy? Does it move? Over 100 m or leaving the building → fibre. Close to heavy electrical equipment → fibre. The device moves or cannot be cabled → radio. Otherwise → twisted-pair copper.

The trap is pushing copper past 100 m because "it worked in the test". Long runs cause errors that come and go, which are far harder to find than a clean failure.

Drills

Answer fast — trust the rule.

Remember

• Copper for desks, glass for distance, radio for freedom.
• Ask: How far? How noisy? Does it move?
• Twisted-pair copper stops at 100 m; beyond that, or near heavy interference, use fibre.