1.4 Bluetooth

Bluetooth is a low-power radio technology aimed at replacing cables for connecting devices. It was originally developed by the Swedish telecommunications manufacturer Ericsson and then formalized by an industry consortium. The name is taken from a Danish king, Harald Bluetooth, who ruled Denmark and Norway in A.D. 936.

The standards for Bluetooth define a low-power radio with a maximum range of 300 feet. The radios are actually on a transceiver microchip to keep size and power consumption to a minimum. Bluetooth uses the 2.45 GHz band of the ISM radio spectrum and divides the band into 79 channels. To further reduce any crosstalk into other ISM bands, Bluetooth devices can change channels up to 1,600 times per second.

Bluetooth is becoming widely available on mobile phones and PDAs, and one of its "killer" applications is hands-free wireless headsets for mobile phones. Bluetooth is also a popular way to "tether" a notebook computer to a cellular phone, which allows you to connect to the Internet even when an 802.11 network is not available (because current cellular data speeds are much slower than Bluetooth, Bluetooth's relatively slow speeds are not the limiting factor). Bluetooth adapters are available for PDAs, desktops, and notebooks . There are some printers and keyboards available that use Bluetooth to communicate with the host device as well.

Compared to Wi-Fi, Bluetooth speeds are not impressive, but they are quite useful for transferring small amounts of data. Download speeds can max out at 720 kbps with a simultaneous upload speed of 56 kbps. Every Bluetooth device can simultaneously maintain up to seven connections, making a personal Bluetooth LAN a real possibility.