EXAMPLE- 5. Radar limit line for control 25. "Low ALT" flashes to indicate when an aircraft"s predicted descent places the aircraft in an unsafe proximity to terrain. (Note: this feature does not function if the aircraft is not squawking Mode C. When a helicopter or aircraft is known to be operating below the lower safe limit, the "low ALT" can be changed to "inhibit" and flashing ceases.) 6. Obstruction (video map) 26. NAVAIDs 7. Primary radar returns of obstacles or terrain (can be removed by MTI) 27. Airways 1. Areas of precipitation (can be reduced by CP) 2. Arrival/departure tabular list 3. Trackball (control) position symbol (A) 4. Airway (lines are sometimes deleted in part) 8. Satellite airports 9. Runway centerlines (marks and spaces indicate miles) 10. Primary airport with parallel runways 11. Approach gates 12. Tracked target (primary and beacon target) 13. Control position symbol 14. Untracked target select code (monitored) with Mode C readout of 5,000" 28. Primary target only 29. Nonmonitored. No Mode C (an asterisk would indicate nonmonitored with Mode C) 30. Beacon target only (secondary radar based on aircraft transponder) 31. Tracked target (primary and beacon target) control position A 32. Aircraft is squawking emergency Code 7700 and is nonmonitored, untracked, Mode C 15. Untracked target without Mode C 33. Controller assigned runway 36 right alternates with Mode C readout (Note: a three letter identifier could also indicate the arrival is at specific airport) 16. Primary target 34. Ident flashes 17. Beacon target only (secondary radar) (transponder) 35. Identing target blossoms 18. Primary and beacon target 36. Untracked target identing on a selected code 19. Leader line 37. Range marks (10 and 15 miles) (can be changed/offset) 20. Altitude Mode C readout is 6,000" (Note: readouts may not be displayed because of nonreceipt of beacon information, garbled beacon signals, and flight plan data which is displayed alternately with the altitude readout) 21. Ground speed readout is 240 knots (Note: readouts may not be displayed because of a loss of beacon signal, a controller alert that a pilot was squawking emergency, radio failure, etc.) 22. Aircraft ID 23. Asterisk indicates a controller entry in Mode C block. In this case 5,000" is entered and "05" would alternate with Mode C readout. 24. Indicates heavy 38. Aircraft controlled by center 39. Targets in suspend status 40. Coast/suspend list (aircraft holding, temporary loss of beacon/target, etc.) 41. Radio failure (emergency information) 42. Select beacon codes (being monitored) 43. General information (ATIS, runway, approach in use) 44. Altimeter setting 45. Time 46. System datrea 4-5-4 Surveillance Systems