Northern Airborne Technology AA21-4xx - Manual (Page 40)

SM34 Rev. 4.00 AA21-400 Cabin PA System Manual
Nov 10, 2003 Page 3-2
ENG-FORM: 806-0105.DOT
CONFIDENTIAL AND PROPRIETARY TO NORTHERN AIRBORNE TECHNOLOGY LTD.
3.4.2 Input Function Selection
The Input Function switch is a two-position, locking switch on the front of the AA21-400
that is used to select between PA and Radio operation. When PA is selected, RADIO is
disabled, and vice versa. It is good practice to set this switch to PA when operating the
siren to avoid mixing incoming radio/CD audio with the siren audio output.
Input Function Switch
3.4.2.1 PA
Operation
For external PA/Siren systems or internal paging functions, set the function switch on
the AA21-400 to PA. Key the microphone through the cyclic or hand mic switch, and
speak in a firm, clear manner.
3.4.2.2 Radio
Operation
To set the system for radio rebroadcast functions, set the function switch on the AA21-
400 to RADIO. All audio delivered from the source (typically pilot’s or copilot’s headset)
will be broadcast from the PA system or internal speaker.
3.4.3 Volume Control
Volume Control
The volume control knob (VOL) on the front of the AA21-400 is used to adjust the level
of the selected output. Rotating the knob cw will increase the volume, and ccw will
decrease it. For external paging and rebroadcast operations, the volume should always
be set between half and full level. The setting for internal paging must be determined
by experiment to provide the desired coverage in the passenger area and to prevent
feedback.