HFP

Hands-Free Profile (HFP) is a Bluetooth profile that enables voice communication between a Bluetooth-enabled telephone and a hands-free peripheral such as a car kit or wireless headset. It defines how devices control calls and transfer audio over a Bluetooth link, allowing users to make, answer, or end calls, and to manage audio routing without touching the phone.

In HFP, two roles are defined: the Audio Gateway (AG) and the Hands-Free (HF) unit. The AG provides the telephony service and interacts with the mobile network, while the HF unit offers the user controls, microphone input, and loudspeaker output. In consumer setups, the mobile phone typically plays the role of the AG and the car’s system or headset plays the HF role.

Key capabilities include call setup and management (answer, hang up, dial, last-number redial, caller ID, call hold and multiparty conferencing), basic audio routing, and status indicators such as service availability, signal strength, battery level, and current call state. The profile also supports indicators and events to monitor phone state and network conditions.

HFP uses SCO-based audio links and traditionally supports narrowband speech. Some later versions, notably HFP 1.6, add Wideband Speech support using the mSBC codec, enabling higher audio quality for calls when both devices support it.

The Bluetooth Special Interest Group maintains HFP as part of the Bluetooth telephony suite. It is widely implemented in mobile phones, car hands-free systems, and Bluetooth headsets, contributing to interoperability across brands and devices.