 Tests of the CVR in the aircraft revealed no discrepancies in the CVR's electrical and recording systems.The CVR tape can be erased by means of the bulk-erase feature on the CVR control panel located in the cockpit.This feature can be activated only after the aircraft is on the ground with its parking brake engaged.In a deposition taken by the Safety Board, the captain stated that he usually activates the bulk-erase feature on the CVR at the conclusion of each flight to preclude inappropriate use of recorded conversations.