Passenger service unit

A passenger service unit (PSU) is an aircraft component situated above each row in the overhead panel above the passenger seats in the cabin of airliners. Among other things, a PSU contains reading lights, loudspeakers for announcements, illuminated signs (to remind people that the aircraft is a no-smoking zone and to wear a seatbelt), buttons to call for assistance (though these are mounted on the armrest on some aircraft), air condition vents, and automatically deployed oxygen masks in case of cabin depressurisation. These are not found on the smallest of feederliners, or on older aircraft. ^{[citation needed]}

v t e Aircraft components and systems
Airframe structure	Aft pressure bulkhead Cabane strut Canopy Crack arrestor Cruciform tail Dope Empennage Fabric covering Fairing Flying wires Former Fuselage Hardpoint Interplane strut Jury strut Leading edge Lift strut Longeron Nacelle Rib Spar Stabilizer Stressed skin Strut T-tail Tailplane Trailing edge Triple tail Twin tail V-tail Vertical stabilizer Wing root Wing tip Wingbox
Flight controls	Aileron Airbrake Artificial feel Autopilot Canard Centre stick Deceleron Dive brake Dual control Electro-hydraulic actuator Elevator Elevon Flaperon Flight control modes Fly-by-wire Gust lock HOTAS Rudder Rudder pedals Servo tab Side-stick Spoiler Spoileron Stabilator Stick pusher Stick shaker Trim tab Wing warping Yaw damper Yoke
Aerodynamic and high-lift devices	Active Aeroelastic Wing Adaptive compliant wing Anti-shock body Blown flap Channel wing Dog-tooth Drag-reducing aerospike Flap Gouge flap Gurney flap Krueger flap Leading-edge cuff Leading-edge droop flap LEX Slats Slot Stall strips Strake Variable-sweep wing Vortex generator Vortilon Wing fence Winglet
Avionic and flight instrument systems	ACAS Air data boom Air data computer Aircraft periscope Airspeed indicator Altimeter Annunciator panel Astrodome Attitude indicator Compass Course deviation indicator EFIS EICAS Flight management system Glass cockpit GPS Head-up display Heading indicator Horizontal situation indicator INS ISIS Multi-function display Pitot–static system Radar altimeter TCAS Transponder Turn and slip indicator Variometer Yaw string
Propulsion controls, devices and fuel systems	Autothrottle Drop tank FADEC Fuel tank Gascolator Inlet cone Intake ramp NACA cowling NACA duct Self-sealing fuel tank Splitter plate Throttle Thrust lever Thrust reversal Townend ring War emergency power Wet wing
Landing and arresting gear	Aircraft tire Arrestor hook Autobrake Conventional landing gear Drogue parachute Landing gear Landing gear extender Oleo strut Tricycle landing gear Tundra tire
Escape systems	Ejection seat Escape crew capsule
Other systems	Aircraft lavatory Auxiliary power unit Bleed air system Deicing boot Emergency oxygen system Environmental control system Flight recorder Hydraulic system Ice protection system In-flight entertainment system Landing lights Navigation light Passenger service unit Ram air turbine

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