54Basic Operation2. Turn the Small knob to change characters. Turn the Large knob to move to the next character. Pressthe CLR key to delete a character.3. Press the Menu/Enter key to end editing and save the values.GroundWhen the Ground selection is pressed the GTX 33 or 330 will be placed in Ground mode where the transpon-der operation will operate normally except no Mode A or C replies are allowed. Squitter replies to discretelyaddressed Mode S interrogations are allowed. GND will be annunciated to the left of the squawk code onthe GNS 480. GND mode also allows the GTX 33 and 330 to transition to ALT based on the GTX criteria forground to airborne determination.Manually Select a Squawk Code1. Press the CRSR in or turn the Large knob to activate squawk code editing. Numbers 0 - 7 will bedisplayed adjacent to the Smart and Line Selection keys.2. Press the key for the desired number. After pressing a numbered key, the next number to the right willbe active for editing.or1. Change the number value with the Small knob and move to the next number with the Large knob.2. After selecting the fourth number, turning the Large knob or pressing Menu/Enter key will endediting.3. You can press the CRSR knob while editing to cancel any changes.NOTE: The current squawk code will be replaced by four yellow dashes, if the remote tran-sponder was never established. The last valid squawk code used will be displayed in yellow, ifcommunication with the transponder is lost while in use.Selecting the transponder squawk code.XPDR
