Just an update - FYI, if the transponders don’t have a Dynon label on them they are the Trig only units which include the encoder. The Dynon versions don’t have an encoder, and rely on their EFIS with inbuilt encoder, & have both labels ie Trig & Dynon On their units.
As I understand it, Trig messed up the numbering of their TT21/ TT22 units during certification & were unable to change them back.
So they are stuck with -
TT22 is a Class 1 Txpdr - which is similar to the tagged Dynon 261. (higher power & meets IFR specs)
TT21 is a class 2 Txpdr - which is similar to the tagged Dynon 262. ( lower power).