The Trimble/ FreeFlight TNL-2101 I/O is a GPS Receiver Display unit that holds up to 250 user waypoints and flight plans with 40 waypoints each. The Dzus mounted TNL-2101 consists of a top case, circuit card assemblies, bottom case, and the display panel. The TNL-2101 uses global positioning system (GPS) signals to track aircraft position and velocity as well as to provide flight planning and waypoint navigation features. The annunciator lights on the TNL-2101 provide system messages, current navigation mode, and parallel track selector.

The TNL-2101 is controlled by the mode keys, function keys, and selector knobs. The NAV key accesses the navigation information, WPT accesses the waypoint data base, FPL for flight planning, CALC for performing E6B calculations, AUX auxiliary function and APT/VOR performs the 20 nearest airport function. The TNL-2101 is 3.00 inches high, 5.75 inches wide, 7.68 inches deep and weighs 3.25 pounds. The TNL-2101 operates up to an altitude of 50,000 feet and in the temperature range of -20°C to +55°C. The TNL-2101 has a power requirement of 28VDC. The TNL-2101 has variations between black or gray faceplates and some with night vision lighting.