Bluetooth (BT) is an industry standard short-distance (up to 10 meters) wireless communications protocol operating at 2.4 GHz. It can optionally use a higher power transmission to achieve distances up to 100 meters. The NXT utilizes the 10 meter option.
BT includes not only the low-level radio transmission (at 2.5 GHz) but also several higher layer message protocols (or profiles) designed for different applications. There are over 25 different BT profiles currently defined. Some of the more popular profiles include:
- The Serial Port Profile (SPP) is used to provide wireless emulation of a conventional RS-232 serial communications cable. This is the only protocol supported on the NXT.
- The Human Interface Device (HID) protocol is used for communication on wireless keyboards and mice. It is also used on some game controllers like the Nintendo Wii or SONY Playstation 3.
- The Headset Profile (HSP) is used to connect wireless headsets to devices like cellphones.
In order to connect two devices via BT, the devices must not only support BT but also support the type of profile that will be used for the connection. The NXT only supports the SPP so that it cannot, for example, directly connect to a Nintendo or Sony game controller.