Passenger service units

Above the passenger seats are Passenger Service Units (PSU). These typically contain reading lights, air vents, and a flight attendant call light. On most narrowbody aircraft (and some Airbus A300s and A310s), the flight attendant call button and the buttons to control the reading lights are located directly on the PSU, while on most widebody aircraft, the flight attendant call button and the reading light control buttons are usually part of the in-flight entertainment system. The units frequently have small "Fasten Seat Belt" and "No Smoking" illuminated signage and may also contain a speaker for the cabin public address system. The PSU will also normally contain the drop-down oxygen masks which are activated if there is a sudden drop in cabin pressure. These are supplied with oxygen by means of a chemical oxygen generator. By using a chemical reaction rather than a connection to an oxygen tank, these devices supply breathing oxygen for long enough for the airliner to descend to thicker, more breathable air. Oxygen generators do generate considerable heat in the process. Because of this, the oxygen generators are thermally shielded and are only allowed in commercial airliners when properly installed they are not permitted to be loaded as freight on passenger-carrying flights. ValuJet Flight 592 crashed on May 11, 1996 as a result of improperly loaded chemical oxygen generators. PSU is an abbreviation in aviation for Passenger Service Unit. This ircraft component is situated above each seat row in the overhead panel above the passenger seats in the cabin of airliners. Amongst other things a PSU contains reading lights, loudspeakers, illuminated signs and automatically deployed oxygen masks and also louvres providing conditioned air. In-flight entertainment (IFE) refers to the entertainment available to aircraft passengers during a flight. In 1936, the airship Hindenburg offered passengers a piano, lounge, dining room, smoking room, and bar during the 2? day flight between Europe and America.[1] After the Second World War, IFE was delivered in the form of food and drink services, along with an occasional projector movie during lengthy flights. In 1985 the first personal audio player was offered to passengers, along with noise cancelling headphones in 1989[citation needed] During the 1990s the demand for better IFE was a major factor in the design of aircraft cabins. Before then, the most a passenger could expect was a movie projected on a screen at the front of a cabin, which could be heard via a headphone socket at his or her seat. The largest manufacturers of IFE systems are Panasonic Avionics Corporation, Thales Group, Rockwell Collins and LiveTV.[citation needed] Design issues for IFE include system safety, cost efficiency, software reliability, hardware maintenance, and user compatibility. The in-flight entertainment onboard airlines is frequently managed by content service providers.