Northern Airborne Technology AA21-4xx - Manual (Page 13)

SM34 Rev. 4.00 AA21-400 Cabin PA System Manual
Section 1.0 Description
1.1 Introduction
This manual contains information on the AA21-400 Cabin PA System.
Information in this section consists of purpose of equipment, features and specifications.
1.2 Purpose of Equipment
The AA21-400 Cabin PA control unit is designed to provide centralized control for an
aircraft’s internal and external PA systems. The design is contained in one panel-
mounted unit, with an illuminated faceplate. All audio and keylines are interfaced to
existing aircraft audio systems. Front panel switches provide selection of the various
operational modes of the AA21 and a potentiometer provides output volume control.
1.3 Features
The AA21-400 provides selection and control of internal and/or external PA system(s)
installed in an aircraft. The integrated 25 W speaker driver circuit is designed to drive
one 8
Ω speaker arrangement for internal paging. The AA21-400 also provides a low-
level audio signal output that drives the input on a remote mounted power amplifier. The
output is designed to drive the NAT PA110/220 or PA250/700 series amplifiers. The
AA21-400 provides generation of wail and yelp siren audio on the low level output when
selected on the front panel.
A ‘+3 dB’ function allows the output level of the system to be varied by 3 dB. When the
input control line is grounded, the output is reduced by approximately 3 dB, and
removing the ground returns the system to full output.
Thermal protection is designed into the intermediate and final stage amplifiers to protect
the unit during very hot or extended high power operating conditions.
Four front panel switches provide selection of the various operational modes of the
AA21-400 as described in Section 3 of this manual (Operation).
Nov 10, 2003 Page 1-1
ENG-FORM: 800-0106.DOT
Amendment #2 May 24, 2006
CONFIDENTIAL AND PROPRIETARY TO NORTHERN AIRBORNE TECHNOLOGY LTD.