Original sentence: Black boxes are often poorly maintained, because they are not critical to flight and have six-year batteries, although normally powered from the aircraft generators.Digital FDRs usually eavesdrop on the aircraft's fly-by-wire main data bus.Emergency locator transmitter automatic signal from an aircraft crash.In aircraft, the flight data recorder (FDR) and the cockpit voice recorder (CVR) are used to record aircraft and pilot behavior, and cockpit noise, in order to analyze accidents, and are often called "black boxes" by the news media.In commercial airliners a microphone is usually mounted above and between the two pilots, in addition to three headset microphone inputs.The cockpit voice recorder (mandatory in commercial aircraft in the USA since 1965) does not store an entire day of data.The system uses multiple microphones to collect all 'noise' in the cockpit, not only conversation but also audible warnings, engine noise, and other mechanical sounds.There are 88 parameters required as a minimum by current US federal regulations (only 29 were required until 2002), but some systems monitor up to 300 variables.To aid in locating them after an incident the boxes are usually bright orange or yellow, not black
Edited sentence: Black boxes are often poorly maintained, because they are not critical to flight and have six-year batteries.Digital FDRs usually eavesdrop on the aircraft's main data bus.In aircraft, the flight data recorder (FDR) and the cockpit voice recorder (CVR) are used to record aircraft and pilot behavior in order to analyze accidents, and are usually called "black boxes" by the news media.In commercial airliners the microphone is usually mounted above and between the two pilots.The cockpit voice recorder (mandatory in the USA since 1965) does not store an entire day of data.The famous, secondary use is to analyze accidents to prevent future failures.The main purpose of the device is to reduce the manufacturer's liability by correctly assigning blame to the failing assemblies or persons.The system uses a single microphone to collect all 'noise' in the cockpit, not only conversation but also audible warnings, engine noise, and other mechanical sounds.There are 88 parameters required as a minimum by US Federal legislation, but some systems monitor up to 300 variables