If you mean you have an older DSM transmitter, then I don't believe it will work with a DSM2 receiver. DX2, DX3, the modules for other radios, are some examples.

DX2.0 and DX3.0 can be either if memory serves. Early ones are DSM only, believe later models do work with DSM2. Can't remember how to tell them apart. Let us know what you have and likely someone can clarify/confirm.

The other way is backwards compatitable, a DSM2 transmitter will work with a DSM receiver.