Earphone

Bluetooth technology is widely used for short-range voice transmission. While it can be and is used for data transmission, the short range (due to using low power to reduce battery drain) is a limiting factor. A very common application is a hands-free Bluetooth earpiece for a phone which may be in a user’s pocket.

A stereo Bluetooth headset.
There are two types of Bluetooth headsets. Headsets using Bluetooth v1.0 or v1.1 generally consist of a single monaural earpiece, which can only access Bluetooth’s headset/handsfree profile. Depending on the phone’s operating system, this type of headset will either play music at a very low quality (suitable for voice), or will be unable to play music at all. Headsets with the A2DP profile can play stereo music with acceptable quality.[7] Some A2DP-equipped headsets automatically de-activate the microphone function while playing music; if these headsets are paired to a computer via Bluetooth connection, the headset may disable either the stereo or the microphone function.