ระบบอินเตอร์โฟนและเสียงประกาศห้องโดยสาร

ภาพรวม

The cabin interphone and passenger address (PA) system provides the communications infrastructure that allows the flight crew to speak to passengers, cabin crew to communicate with the flight deck, and crew members throughout the cabin to coordinate with one another. It is a seemingly simple system whose importance becomes critical in emergencies: a clear, intelligible PA announcement during a rapid decompression or evacuation can save lives, and a reliable interphone connection between a cabin crew member reporting smoke and the flight deck can enable a crew to initiate emergency procedures minutes faster than alternative communication methods.

Regulatory requirements mandate that an interphone system be installed and functional on every commercial transport aircraft (FAR 25.1423, CS 25.1423), and that the PA system be capable of reaching every passenger regardless of cabin noise conditions. Modern systems integrate with the aircraft's Cabin Intercommunication Data System (CIDS) and, on aircraft with advanced IFE, can deliver crew announcements directly through IFE headphones at a level that overrides passenger content without requiring overhead speaker operation.

หลักการทำงาน

The interphone system is based on a switched audio network — the Cabin Intercommunication Data System (CIDS) or a simpler Selective Calling (SELCAL) matrix — that connects handset stations at each flight attendant seat, each galley, the forward entry area, and the flight deck. Each station has a handset (or headset in some installations) with a push-to-talk switch and a call selector. Pressing a station number on the keypad or rotary selector routes the audio connection to that specific station; all-call or zone-call modes enable simultaneous communication to multiple stations.

The PA system uses the same audio infrastructure but routes through cabin loudspeakers — typically one speaker per two rows in economy class, positioned in the overhead PSU or ceiling panels — at a volume level calibrated to overcome cabin ambient noise (typically 70–80 dB in cruise). The PA microphone at the flight deck or galley stations applies audio processing including noise cancellation and automatic gain control to ensure intelligible announcements even when the speaker is in a noisy environment. Pre-recorded announcement capability allows airlines to store and replay standardized safety, boarding, and arrival messages in multiple languages at the touch of a button.

ส่วนประกอบหลัก

• Attendant Handset: Corded handset at each crew station with number keypad or push-button call selector, push-to-talk switch, and volume control; ruggedized for repeated daily use.
• Cabin Intercommunication Data System (CIDS) Director: Central processor managing all interphone, PA, and cabin data functions; typically a Line Replaceable Unit (LRU) in the avionics bay or forward electronic equipment area.
• PA Amplifier: Audio amplifier driving all cabin and lavatory speakers; typically 50–200W depending on aircraft size, with automatic level control for cabin noise compensation.
• Cabin Speakers: Flush-mounted in PSU or ceiling panels; small-diameter (3–4 inch) full-range drivers engineered for intelligibility over cabin background noise rather than high-fidelity reproduction.
• Chime and Attention Tone Generator: Produces the characteristic single or triple chime tones that precede crew call and PA announcements; specific tone patterns have standardized meanings (e.g., two-tone high-low chime for priority call on Boeing aircraft).
• Pre-Recorded Announcement System (PAS): Digital audio storage and playback allowing cabin crew to select and broadcast pre-approved safety briefings, boarding music, and arrival announcements.

การใช้งานในอากาศยาน

On the Boeing 737-800, the interphone system is a straightforward SELCAL matrix with handsets at the forward and aft attendant stations and the flight deck. Three-zone PA covers economy and any forward premium seats. The Airbus A320-200 uses the CIDS architecture, which integrates interphone, PA, cabin lighting control, and door/slide monitoring status data into a single avionics unit, simplifying the cabin wiring harness significantly.

The Boeing 787-9 features the most advanced CIDS implementation, with wireless crew communication options being introduced by some operators, IFE headphone PA integration, and digital pre-recorded announcement capability in up to 15 languages stored in the CIDS director. The system supports priority override functions where a flight deck PA automatically overrides any IFE audio and crew interphone traffic.

ข้อดีและข้อจำกัด

A well-designed interphone and PA system contributes directly to safety by enabling rapid, clear communication during abnormal events. The integration of PA with IFE headphone systems dramatically improves intelligibility for passengers wearing noise-cancelling headphones — a growing proportion of long-haul passengers — who may not hear overhead speaker announcements at normal volumes.

Limitations include vulnerability to cabin noise: on regional turboprop aircraft and older jet types without digital noise compensation, PA intelligibility can be poor in cruise, a significant safety concern for emergency announcements. Handset reliability is a persistent maintenance issue; the retractile cord connecting the handset to the station is subjected to thousands of extension/retraction cycles and is a common fault point. Integration with IFE systems, while beneficial, adds software complexity and requires careful certification to ensure IFE faults cannot compromise the independently certified PA system.