OPERATIONS MANUAL

Communications
ACP:
DME Morse codes
A DME station uses 1350 Hz tones, unlike VOR and ILS stations
which use 1020 Hz tones. Moreover, a DME tone is louder than VOR
and ILS tones, and it sounds only in every fourth transmission cycle;
VOR and ILS tones are transmitted in the first three cycles only. These
specifications allow the pilot to identify a DME station when it is
paired with another station. Lastly, whether or not a certain DME tone
is audible depends on the ACP settings, but also on the selected ND
display modes:
• Morse codes of ILS-paired DME stations are audible on ILS L when
the captain’s ND is in APP display mode, or are audible on ILS R
when the first officer’s ND is in APP display mode. ILS C provides
no DME monitoring.
• Morse codes of non-ILS-paired DME stations are audible on VOR L
when the captain’s ND is not in APP display mode, or are audible on
VOR R when the first officer’s ND is not in APP display mode.
In all other cases, DME tones cannot be heard; that is, in the fourth
transmission cycle, no tone is audible at all.
The ND display modes can be selected on the EFIS control panels and
on the left and right CDUs. For more details refer to chapter Flight
Instruments.
Interphone Speakers:
Captain’s interphone speaker,
located on left side panel; first
officer’s interphone speaker is
installed on opposite side panel
(interphone speakers are not
displayed in the simulator).
Volumes are controlled by
ACPs. When a PTT switch
is pushed, both interphone
speakers are muted.
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