Garmin SL30 Pilot's Manual page 33

Advanced Operation
Nav Mode
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The T/F button selects the To or From radial display. If the VOR radial display is not
currently shown, press T/F to show the radial display. When the VOR radial is displayed,
pressing T/F will toggle between the Bearing To and Radial From the VOR. This button is not
functional if a localizer frequency is selected on the active channel.
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