Eric Greenwell wrote:
(Garrecht, MicroAir, Funkwerk, Becker...). You need a level 2, class 1
transponder, be sure not to confuse level and class!

Be sure to look at the Trig TT21 Mode S transponder - more like $2000 -
and with some ADS-B out capability.

Again: Make sure the transponder is class 1! The TT21 is class 2.

BTW: Most transponders are "ADB ready". Whatever this means.