Cockpit Voice Recorders save approximately two hours of cockpit conversations that can be used in conjunction with Flight Data Recorders to ascertain the cause of accidents.
There are four channels of recordings. An area microphone, the capt's audio system, the F/O's audio system, an observers system or the cabin public address system.
Flight data recorder information is usually downloaded at regular intervals with the use of components such as the WQAR
There is no need to monitor CVR recordings continuously, but functionality of the units must be checked periodically. Maintenance will perform a CVR download which is used by engineering to verify all recording operations are valid.