Signals transmitted using Bluetooth, a technology for connecting devices wirelessly across short distances, reach about 32 feet. Bluetooth transmission is relatively weak so that it does not interfere with TVs and other electronics. It uses about 1 milliwatt of power, while mobile phones typically use about 3 watts.
Bluetooth can go through walls and does not require that the devices being connected are within sight of each other. It transmits at a frequency of around 2.45 gigahertz, which has been reserved through an agreement among countries for use by devices in medicine, science and industry. Devices that share frequency with Bluetooth include garage-door openers, some cordless phones and baby monitors. Bluetooth devices are designed to avoid interference with other devices using the same frequency.
Bluetooth was invented by telecommunications company Ericsson in 1994. It allows for connecting several devices at the same time. The word Bluetooth comes from the 10th-century Scandinavian king Harald Bluetooth, who united several tribes in Denmark into one kingdom.
The Bluetooth Special Interest group manages the Bluetooth protocol. The group has more than 20,000 companies as members in industries including consumer electronics, telecommunications and computers. The group manages the qualification program for manufacturers wishing to use Bluetooth and oversees trademark protection. Manufacturers whose devices are marketed as using Bluetooth must follow certain quality standards that the group creates and oversees.