Bluetooth

Bluetooth is a wireless standard that links devices which are close together, and it needs very little power to do it. Two devices connect directly to each other, with no network in between.

What Bluetooth is used for

Bluetooth suits peripherals – devices that work alongside another device rather than joining a network. A games controller connected to a console, or a small handheld scanner in a shop sending each item's code straight to the till, both use it. The link is direct, so the scanner never has to join the shop's network to do its job, and it still works in a building with no Wi-Fi at all.

It also handles short file transfers between two devices sitting close together, such as a tablet sending one page of homework to a printer standing beside it. Sending small amounts of data over a short distance is exactly what Bluetooth is built for.

Why low power matters

Bluetooth uses very little power, which is why it turns up in equipment running from a small battery. A wireless door sensor on a garden gate, powered by a coin cell, can send an alert to a phone for months without a new battery, because the radio it uses sips electricity. A high-power radio would flatten the battery in hours.

Where Bluetooth stops

Two limits hold it back. It has a very short range, so the two devices must stay near each other, and its bandwidth is lower than Wi-Fi, so it carries small bursts of data rather than large amounts at speed.

That is why Bluetooth is a poor fit when computers must be joined into a local area network. A LAN has to link many machines across a room or a whole building and move sizeable files between them; Bluetooth is built for two devices close together, so Ethernet or Wi-Fi is used for the LAN instead.