Garmin GNS 480 Installation Manaul page 115

3.3.2.4 Interface Checkout
This section describes checks that can be carried out to verify that systems interfacing to the GNS 480 are
communicating properly.
3.3.2.4.1 GNS 480 Message Audio
The GNS 480 can annunciate audio messages through an audio panel. This check verifies that the audio
connection from the GNS 480 to the audio panel is functional. Prior to proceeding with this check, ensure
that the audio panel is set to annunciate the GNS 480 message audio. If the following steps do not perform
correctly, check the electrical connections and AMA volume setting.
1. Go to the System Configuration page. This page is accessed by pressing the FN key repeatedly until
the SYS smart key is displayed. The SYS smart key is then pressed, followed by the CNFG smart
key, if necessary.
2. While on the System Configuration page, rotate the large, outer knob to scroll down to the Msg Tone item
and verify that it is set to ON. If it is set to OFF, push the small, inner knob in to edit the setting and rotate
the small, inner knob to change the setting to ON. Press the MENU/ENTER key to accept the setting.
3. Rotate the large, outer knob and scroll up to the Mag Var setting. Press the small, inner knob in to edit
the setting and rotate the small, inner knob to change the setting to MANUAL. As soon as the setting is
changed to MANUAL the GNS 480 will display a "Using Manual Mag Var" message and play the message
tone. Verify that this tone is heard over the audio system.
4. If necessary, adjust the Message Audio volume level as described below and replay the tone to verify the new
setting.
5. Return the Mag Var setting to AUTO.
Message Audio Volume Level Adjustment
The message audio volume was preset at the factory to a typical audio level. The level can be adjusted as
follows:
1. Press the COM bezel key, followed by the MENU/ENTER key to display the COM menu. Press the
AUDIO line select key to display the volume adjustment window. The audio message (AMA)
selection will be selected. Rotate the PWR/VOL knob or the small, inner knob to adjust the audio
message volume level. The audio message level is displayed as a horizontal bar, showing the level
from zero to 100%.
2. Press the MENU/ENTER key when done.
3.3.2.4.2 Baro Correction Potentiometer
The GNS 480 can receive baro correction from an external potentiometer. This check verifies that the
GNS 480 is receiving baro correction data from the altimeter. Ensure that the GNS 480 is turned on. If the
following steps do not perform correctly, check the electrical connections and configuration setup.
1. Check the baro correction using the Configuration page. This page is accessed by pressing the FN
key twice, causing the SYS smart key to be displayed. The SYS smart key is then pressed, followed
by the CNFG smart key, if necessary. The baro correction is the first item on the list (Baro Correct.).
2. Verify that the baro correction decodes properly from 28.10 to 31.00 "Hg (952 to 1050 mB). The
value displayed on the GNS 480 should be within ± 0.03 "Hg (±1 mB) of the altimeter setting.
GNS 480 (CNX80) Installation Manual
Post-Installation Configuration & Checkout
560-0982-01 Rev L 3-35