The 480 is listed for some transponders, including the GTX33ES.
GDL-88, GTX-33x w/ES, GTX-330x, GTX-3000 (GTXmodels require appropriate S/W rev)
Garmin GTN 625/635/650, GTN 725/750, GIA 63W, GNC 420W/420AW, GNS 430W/430AW/480/530W/530AW, GPS 175, GPS 400W/500W (w/ or w/o TAWS) (all require...