What signs are included in a Passenger Service Unit (PSU)?

The Passenger Service Unit (PSU) is an essential component found above passenger seats in an aircraft, designed primarily to provide critical information and services to passengers. The inclusion of fasten seatbelt and no smoking signs within the PSU serves crucial safety functions.

The fasten seatbelt sign signals passengers to secure their seatbelts, particularly during takeoff, landing, or turbulent conditions, ensuring passenger safety onboard. The no smoking sign prohibits smoking in the cabin, which is vital for maintaining a safe environment, as smoking can pose serious fire hazards in an aircraft.

Other options, while related to passenger services and safety, do not specifically represent the standard components found in a PSU. Emergency exit signs and crew alert signals are located throughout the aircraft but are not part of the PSU itself. Electronic display screens and flight information displays are typically found in different locations within the aircraft and are not a standard component of the PSU. Hence, the signs for fastening seatbelts and no smoking are the fundamental elements included in the Passenger Service Unit.