Northern Airborne Technology AA21-4xx - Manual (Page 39)

SM34 Rev. 4.00 AA21-400 Cabin PA System Manual
Nov 10, 2003 Page 3-1
ENG-FORM: 806-0105.DOT
CONFIDENTIAL AND PROPRIETARY TO NORTHERN AIRBORNE TECHNOLOGY LTD.
Section 3.0 Operation
3.1 Introduction
Information in this section consists of the functional and operational procedures for the
AA21-400 Cabin PA system.
3.2 Operation Specifics
The AA21-400 Cabin PA system provides a central adjustment for internal and/or
external aircraft paging functions. The AA21-400 is a self-contained amplifier that
directly drives the cabin speaker(s) and/or the external PA system amplifier. When
turned on, the system is ready for operation and will accept audio feeds or a
microphone input. An internally generated siren is also available in WAIL or YELP
modes. When the AA21-400 is turned on, a 28 Vdc switched signal is generated. This
signal is used to turn on the PA amp relay (if connected in system). The high current
DC power to operate the PA110/220 or PA250/700 is supplied by the aircraft.
3.3 Techniques of Voice Transmission
To successfully project the human voice over long distances, it is necessary to develop
a microphone technique different from the usual conversational manner. Place the
microphone with the upper lip touching the mouthpiece and talk clearly and distinctly,
with increased emphasis. Separate each word with noticeable pauses and keep the
voice level constant. A medium pitched voice is more easily understood and carries
farther than a bass voice.
3.4 Basic Operation
3.4.1 Power up
To activate the AA21-400 Cabin PA system, flip the POWER toggle switch up to the ON
position. The LED adjacent to the switch should illuminate.
Power Switch Indicator LED