Altitude Decoder Test Page - Garmin 155XL Maintenance Manual

1. Press the CRSR key.
2. Rotate the outer function knob until the External Switches Test Page is displayed (Figure 5-5).
3. Activate APPR SELECT (J1-9). The External Switches Test Page should display 'APPR ON.'
4. Deactivate APPR SELECT (J1-9). The External Switches Test Page should display 'APPR OFF.'
5. Activate OBS HOLD (J2-13). The External Switches Test Page should display 'HOLD ON.'
6. Deactivate OBS HOLD (J2-13). The External Switches Test Page should display 'HOLD OFF.'
7. Activate the remote enter position. The External Switches test page should display 'REMOTE ENT
ON'.
8. Deactivate the remote enter position. The External Switches test page should display 'REMOTE
ENT OFF'.
Altitude Decoder Test
This test exercises each altitude data line individually. Most altitude codes presented will be invalid; however,
input line C1 valid (J2-21) and input line C2 valid (J2-22) indicate altitude readings of -800 and -1000 feet,
respectively.
1. Rotate the outer function knob until the Altitude Decoder Test Page is displayed (Figure 5-6).
2. Activate input line D4. Verify that D4 on the Altitude Decoder Test Page indicates '1'. All other
altitude inputs should still indicate '0'.
3. Continue to step through input lines A1, A2, A4, B1, B2, B4, C1, C2, and C4. Verify that only one
input line (A1, A2, A4, B1, B2, B4, C1, C2, or C4) indicates '1' for each switch position. All other
altitude inputs should still indicate '0'.
5-8
Figure 5-6. Altitude Decoder Test Page
190-00067-25 Rev D