Funny, Spektrum reps say the older receiver are backwards compatible. I know mine work with my transmitters, DX7 & DX8 . In fact I've even used the Older "Orange receiver" with the newer DX8 transmitters. What does not work (out of the box) is a receiver that has more channels than the transmitter. But, it could be that I've been ripped off and neither transmitter is DSM2 or DSMX.. Does anyone know how to determine this?