Garmin GPS 500 Pilot's Manual & Reference page 171

Table 10-2 shows the possible TERRAIN alert types with corresponding annunciations.
TERRAIN Failure
TERRAIN Inhibited
TERRAIN Not Available
Required Terrain Clearance (RTC) Advisory
Required Terrain Clearance (RTC) Caution
Imminent Terrain Impact (ITI) Advisory
Imminent Terrain Impact (ITI) Caution
Required Obstacle Clearance (ROC) Advisory
Required Obstacle Clearance (ROC) Caution
Imminent Obstacle Impact (IOI) Advisory
Imminent Obstacle Impact (IOI) Caution
Premature Descent Alert (PDA)
190-00181-60 Rev. G
Alert Type
Table 10-2 TERRAIN Alert Summary
GPS 500 Pilot's Guide and Reference
Annunciation Pop-Up Alert
(FLASHING)
(FLASHING)
(FLASHING)
(FLASHING)
(FLASHING)
(FLASHING)
(FLASHING)
(FLASHING)
SECTION 10
TERRAIN
None
None
None
10-5