What is a Cockpit Voice Recorder (CVR)? Use of Cockpit Voice Recorder (CVR)? Brief description about Cockpit Voice Recorder (CVR)?

A Cockpit Voice Recorder (CVR) is a flight recorder used to record the audio environment in the flightdeck of an aircraft for the purpose of investigation of accidents and incidents. This is typically achieved by recording the signals of the microphones and earphones of the pilots headsets and of an area microphone in the roof of the cockpit. The current applicable FAA TSO is C123b titled Cockpit Voice Recorder Equipment.
Where an aircraft is required to carry a CVR and utilises digital communications the CVR is required to record such communications with air traffic control unless this is recorded elsewhere. It is at present (2005) a requirement that the recording duration is a minimum of thirty minutes, but it is recommended that it should be two hours

What is a Cockpit Voice Recorder (CVR)? Use of Cockpit Voice Recorder (CVR)? Brief description about Cockpit Voice Recorder (CVR)?