Trig TT-21 Xpdr
Spoke with Bruce at Mid Continent Instruments and Avionics, trigsupport@mcico.com, 800-821-1212.
The TT21 is an older model that the FAA won't approve. They will upgrade it with a TT22 circuit board for $950 vs. $2250 for an all-new TT22. Includes a new 2-year warranty.