Bluetooth is a wireless protocol for exchanging data over short distances from fixed and mobile devices, creating personal area networks.
There are two important parameters of Bluetooth devices – class and supported profiles.
“Class” signifies the distance at which a Bluetooth connection is possible. Most mobile devices are Class 2, which means they have a range of up to 10 m. Class 1 devices are rare and have a range of up to 100 feet.
A “profile” is a type of Bluetooth connection. The most common are the Headset (HSP) and Handsfree (HFP) profiles that enable the device to connect to a wireless headset or handsfree.
Some other profiles are OBEX (OBject EXchange) which allows transfer of files, contacts and events; A2DP, which adds support for streaming of stereo sound and AVRC, which allows remote control of playback.
aptX
The aptX audio codec is a proprietary audio codec compression algorithm, which allows the real-time streaming of high quality stereo audio over a Bluetooth A2DP connection between a source device and the accessory device.
aptX technology must be incorporated in both the source and the accessory device for it to have any effect. Full backwards compatibility however allows audio streaming even when one of the devices is not aptX compatible, though in this case, the connection won’t benefit from the technology.
EDR (Enhanced Data Rate)
An optional part of the Bluetooth specification that provides a faster data rate (speed) and possibly improved battery life. Not all Bluetooth devices support EDR and will depend on the Bluetooth version and supported profiles. Both devices need to support EDR, in which case EDR is used automatically.