Northern Airborne Technology AA83-001 rev.4.10 - Manual (Page 32)

AA83-001 InterMUSIC™ Stereo Intercom System Manual SM09-2 Rev. 4.10
The pilot has no ICS or music operation when selected to PIL ISO, and all his signals
are presented in mono format during this mode.
This mode is 'fail-passive', meaning that it requires no power to operate and is the same
mode the box goes into automatically when power is lost to the AA83-001. In this
way, switch over is immediate for the pilot and there is no possibility of lost
communication because of a lack of pilot action. Note that the pilot's boom mic is sent
directly to the radio in this mode, and only a PTT key input is needed to transmit.
3.3.5.3 Tie/Split Operation
The MODE switch has one further position, which can be used in expanded systems for
more complex audio circuits. If an outboard AA82 has been installed (or some other
NAT system with tie line capability), then this switch will open and close the tie line
output to create common or split intercom circuits with the external system.
In all positions other than SPLIT, the ICS tie line is sent to outside systems for common
intercom operation. This can be used for common communication from front to rear (for
example) in a larger aircraft. When set to the SPLIT position, the AA83-001 cuts the tie
line, breaking the two units into individual intercom circuits with isolated conversations.
In this way, many different circuit combinations can be set up, depending on what
device is hooked to the tie line.
With no external unit, the SPLIT position has no function within the AA83-001.
3.3.6 Automatic Fail-safe
In the event of a power failure, automatic fail-safe operation will be activated. This
routes the pilot’s phones, mic audio, and mic PTT directly to the COM radio. Copilot and
passengers will have no ICS, music, or receive functions.
The pilot mic is directly connected to the transceiver mic. Mic bias is provided by the
transceiver, not the AA83-001. The pilot TX keyline is directly connected to the
transceiver.
During receive mode, receive audio is directly connected from the audio source to the
pilot phones, and during transmit mode, the sidetone audio is directly connected from
the audio source to the pilot phones. In both cases, copilot and passengers have no
ICS, music, sidetone, or receive functions.
In the unlikely event of an AA83-001 circuit failure that results in a communication
problem, the automatic fail-safe mode can be enabled by pulling the AA83-001 circuit
breaker.
Note: In Automatic Fail-Safe mode, the receive/sidetone levels may require adjustment
at the audio source.
The pilot should confirm that all aspects of Automatic Fail-Safe operation are
working before accepting the aircraft into service.
Page 3-4 Oct 20, 2004
ENG-FORM: 806-0106.DOT
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