Saab 340B, Operation Manual

Page: 281 / 670

COMMUNICATIONS, PA/INTERPHONE
Description
Aircraft Operations Manual
4/4.1
S2
PAGE 1
Dec 01/15
A/C 380 − up
1. GENERAL
The Passenger Address (PA) and Interphone are
two combined systems, utilizing the same amplifier
unit (PA amplifier) located in the avionics rack.
The PA system provides the passengers with cabin
attendant call buttons which gives a HI chime tone
in the cabin loudspeaker system for attention.
The HI chime tone will also be heard as soon as
”NO SMOKING” or ”SEAT BELT” signs are oper-
ated on/off.
For boarding music etc., an entertainment system
can easily be connected to the PA system.
The Interphone system provides communication via
two interphones, between cockpit and cabin crew
and also for giving messages to the passengers.
There are also three lights PA, CALL and EMER,
which together with HI
− LOW chime tone, alerts the
cockpit/cabin crews about any calls.
The Interphone gives the following communications:
− Cockpit to passenger.
− Cockpit to cabin attendant.
− Cabin attendant to cockpit.
− Cabin attendant to passenger.
The PA system has the following functions:
− Cabin attendant call buttons.
− NO SMOKING/ SEAT BELT signs.
− Loudspeakers for distribution of messages.
− Boarding music/entertainment systems.
2. MAIN COMPONENTS AND SUBSYSTEMS
2.1 PA AMPLIFIER
The PA amplifier basically consists of an amplifier
circuit and a chime generator circuit.
Audio signals from the cockpit and cabin inter-
phones are amplified as well as HI and LOW chime
tones created by the chime generator. HI chime is a
585 Hz tone and LOW chime is a 495 Hz tone. The
PA amplifier also distributes the audio signals out to
the cabin loudspeakers.
The amplifier has two fixed audio levels, one low
level and one increased level for engine/propeller
noise compensation, controlled by engine oil pres-
sure.
2.2 Cockpit/cabin interphone
The similar type of interphones is used in cockpit
and cabin. The handset is provided with noise can-
celling microphone. There are three buttonlights on
top of the cradle, PA, CALL and EMER. The upper
half of the buttonlight is lit to identify the function.
The lower half of the buttonlight will come on to indi-
cate the function in use. The amplifiers for the inter-
phone system are located in the cradles. The cabin
interphone is protected against inadvertent use,
therefore the handset must be released before se-
lecting a buttonlight.
2.3 Loudspeakers
There are eleven loudspeakers in the cabin evenly
distributed above the passenger seats and one in
the lavatory area.