Northern Airborne Technology AA20 - Manual (Page 10)

AA20 Series PA/Siren System
SM33-1 Installation and Operation Manual
Section 2 Rev: 1.00 Issue 4 Page 2-3
ENG-FORM: 805-0115.DOT
CONFIDENTIAL AND PROPRIETARY TO NORTHERN AIRBORNE TECHNOLOGY LTD.
2.4.4 Post Installation Checks
2.4.4.1 Voltage/Resistance Checks
Do not attach the AA20 until the following conditions are met.
Check the following for all models of AA20:
a) Check P101, pins 1 and 2 for +28 Vdc relative to ground.
b) Check P101, pins 14, 15 and 16 for continuity to ground (less than 0.5
Ω).
c) Check P101, pin 3 for the presence of the lamp dimmer voltage.
d) Check P101 pins 4, 5, 6 and 7 for infinite resistance to ground (> 10 M
Ω).
e) Check P101 pin 10 (AA20-030, -050, -050H) or pin 12 (AA20-430) for continuity to ground
(below 0.5
Ω). This ground is installation specific and may be a 'hard' ground or supplied by a
momentary switch (siren/chime trigger).
Check the following for AA20-030 and AA20-430:
f) Check P101, pin 4 for continuity to pin 5 (less than 0.5
Ω).
g) Check P101, pin 6 for continuity to pin 7 (less than 0.5
Ω).
h) Check P101, pin 4 to pin 6 for 8
Ω (speaker connected).
Check the following for AA20-050 and AA20-050H:
i) P101 pin 4 to pin 6 for 8
Ω (speaker connected) or 300 Ω (PA110/220 connected).
j) P101 pin 5 to pin 7 for 8
Ω (speaker connected).
2.4.4.2 Power On Checks
Power up the aircraft’s systems and confirm normal operation of all functions of the AA20. Refer to
Section 3 (Operation) for specific operational details.
a) Turn on all of the radios and other accessories required for this system. Check that the
POWER ON LED on the AA20 illuminates when the power switch is selected to ON.
b) Key the siren using the front panel button and/or remote siren key. The siren should sound
and the level should be at maximum volume (the front panel level control does not affect the
siren). If the siren (rate or tone) needs adjustment use the trimpots on the left side of the
AA20. Refer to section 2.5 for details.
c) Configure the audio system as required to allow connection of the pilot's mic to the PA and
key the cyclic switch for transmit. The mic audio should be heard on the PA speakers. Adjust
the front panel level control for the desired volume.
d) Check preset adjustments are completed before aircraft departure.
Notes: 1. PA audio has priority in the AA20 system, and it will be heard even if the panel switch is
selected to RADIO. Check for correct radio operation and note the volume settings that
produce a suitable external paging level.
2. A faint audio signal may be heard at the speaker (even when the system is not paging) due to
the very high gain of this system and stray coupling in the wiring. It should not be audible in
flight.