Wired Connections

A wired connection links devices using a physical transmission medium — a cable — instead of wireless signals. Data travels along the cable itself, so the devices are physically joined together and nothing is sent through the air.

Three common cables

• Twisted pair copper cable — pairs of copper wires twisted together, carrying data as electrical signals. It is thin and flexible, so it is used for most everyday network links.
• Coaxial cable — a single copper core surrounded by a metal shield, also carrying data as electrical signals. It is thicker and stiffer than twisted pair, so it does not bend around tight corners as easily.
• Fibre optic cable — a thin strand of glass that carries data as pulses of light rather than as electricity.

Each cable type ends in its own connector, so a cable cannot be pushed into a port built for a different type.

Ports and plugs

For a wired connection to work, every device needs a physical port that matches the cable, and the cable must be long enough to reach the rest of the network. A computer usually has an RJ45 port, a rectangular socket that takes a twisted pair cable with an RJ45 plug; a fibre optic port has a different shape and takes a different plug. A device with no port at all, such as a slim tablet, cannot join the network by cable unless you add an adapter.

For example, in a small veterinary surgery, the reception computer, the vet's desktop and a shared printer each have an RJ45 port. One twisted pair cable runs from each port to a switch in the back office, so all three devices are part of the same wired network. A nurse's laptop with no network port would need an adapter before a cable could connect it.