JO 7110.65 5-2-21

TERMINAL

Set altitude filters to display Mode C altitude readouts to encompass all altitudes within the controller's jurisdiction. Set the upper limits no lower than 1,000 feet above the highest altitude for which the controller is responsible. In those stratified positions, set the lower limit to 1,000 feet or more below the lowest altitude for which the controller is responsible. When the position's area of responsibility includes down to an airport field elevation, the facility will normally set the lower altitude filter limit to encompass the field elevation so that provisions of paragraph 2-1-6 , Safety Alert, and paragraph 5-2-15 , Validation of Mode C Altitude Readout, subparagraph b 2 may be applied. Air traffic managers may authorize temporary suspension of this requirement when target clutter is excessive.