737 MAX Flight Crew Operations Manual
Communications -
System Description
5.20.4
MN-FLT-OH-201
Service (Attendant) Interphone System
The service interphone system provides intercommunication between the flight
deck, Flight Attendants, and ground personnel. Flight deck crewmembers
communicate using either a separate handset (if installed) or their related ACP and
any standard microphone.
The Flight Attendants communicate between flight attendant stations or with the
flight deck using any of the attendant handsets. Anyone who picks up a
handset/microphone is automatically connected to the system.
External jacks for use by maintenance or service personnel can be added to the
system by use of the service interphone switch.
Passenger Address System
The Passenger Address (PA) system provides audio input to speakers in the cabin,
allowing announcements and music to be broadcast to the entire passenger cabin.
The speakers are installed in lavatories, the forward galley, near the aft
entry/service doors and in the Passenger Service Units (PSUs). Input is prioritized
by source.
The highest priority audio input source is selected when the flight crew selects
"PA" on the audio control panel and speaks through the boom mic on a headset,
the oxygen mask microphone or the hand-held microphone connected to the
Passenger Address microphone jack on the P8 aft electronic panel. These methods
will preempt all music and other announcements, including announcements
in-progress by Flight Attendants in the cabin.
The second-priority level is announcements made using the Flight Attendant
handsets. A Flight Attendant handset which is already being used to make an
announcement has priority over any other Flight Attendant handset, the PRAM
and entertainment systems.
The third-priority level is the PRAM. The PRAM provides pre-recorded messages
and music over the PA system. Messages from the PRAM can be manually
generated or automatically generated. Manually generated messages have priority
over automatically generated messages, and both of these have priority over music
being provided by the PRAM.
Pre-Recorded Announcement Machine (PRAM)
The PRAM uses pre-recorded announcements to automate the broadcasting of
emergency and informational messages, as well as music, through the public
address (PA) system in the cabin of the aircraft. When a passenger entertainment
system is installed, announcements are also broadcast to each passenger through
entertainment headsets.
March 1, 2021
