Northern Airborne Technology AA9x - Manual (Page 48)

AA9x Series Single Channel Audio Controller
SM56 Installation and Operation Manual
Section 3 Rev: 1.00 Issue 4 Page 3-5
ENG-FORM: 806-0111.DOT
CONFIDENTIAL AND PROPRIETARY TO NORTHERN AIRBORNE TECHNOLOGY LTD.
3.4.1 ICS ISO and/or PLT ISO Annunciators
ICS ISO and/or PLT ISO annunciators indicate that the intercom connection to the other audio controllers
(typically the pilot’s) has been switched off.
3.4.2 ICS CALL Annunciator
ICS CALL annunciator indicates that an ICS CALL switch is active and that the intercom connection
between the audio controllers needs to be restored.
3.4.3 ICS CALL Switch
ICS CALL switch used to signal other audio controllers (typically the pilot’s) that an ‘isolated’ station
needs to communicate with the pilot(s). The output from the switch is normally used to activate a CALL
annunciator and/or a CALL tone.
3.4.4 PAT ON/OFF Switch
PAT ON/OFF (Patient Headphone Audio Select) switch allows the crew to select the patient audio ON or
OFF.
3.4.5 ICS TIE/SPLIT Switch
ICS TIE/SPLIT switch allows for local selection of the intercom connection to other audio controllers in the
aircraft intercom system. In the TIE position, intercom audio is shared with all other audio controllers. In
the SPLIT position, intercom audio to/from all other audio controllers is deselected.
3.5 Emergency Operation (AA95 and AA97 models only)
When the red PILOT ISO EMR/NORMAL mode switch is set to the ISO/EMR position, the pilot is
removed from the ICS bus and connected directly to the selected radios. This mode should be selected in
the event of a box fault or power failure.
In the ISO/EMR mode, all functions are retained by the pilot, except ICS and possibly boom mic
operation. If the box or airframe fault prevents the TX annunciator from lighting during transmit (indicating
a failure in the mic keying circuit), then the hand mic should be used. A power fault of any kind will
prevent the TX annunciator from lighting, giving an immediate indication of failure. If ICS audio is still
available, then the power to the controller has not failed, and loss of the TX light indicates TX switch
failure.
In the ISO/EMR mode, all switches work exactly as they do during NORMAL operation, except for the RX
and ICS volume controls, which have no effect. The ISO/EMR function should be tested prior to flight to
ensure proper operation and allow the radio levels to be set adequately for emergency operation.
Any selected receive audio is switched to the primary user (pilot) in the ‘emergency’ mode, but not to any
passengers in the system. Audio level will be lower than in NORMAL operation because the signals are
obtained directly from the radios, bypassing the electronics in the controller. This is provided for failure
situations that make operation impossible in the NORMAL mode (i.e. loss of power or amplifier failure, etc.).