The Underwater Locator Beacon (ULB) is usually the only part that requires any type of periodic maintenance for most Cockpit Voice Recorders (CVR) and Flight Data Recorders (FDR). This maintenance includes cleaning and testing the ULB every 2 years and replacing the battery every 6 years. It should be noted that some aircraft maintenance programs may include testing and/or bench testing of CVRs or FDRs as part of the aircraft maintenance program.