It is obvious Melanie that there is no data integrity check of any kind there,

So it is obvious too, that Bill needs a lot of reading and experimenting onthe subject, which is difficult by default.

Bill, these modules needs DC balancing. This is what Melanie is telling you. If you don't know or want to do that then choose any other module that is doing it inside the can box. There are some for treu RS-232 communication.

Otherwise you must have to do that using Manchester encoding-decoding along with some kind of error check code.

Start slowly, searching the forum. All are there. But give some more details on the project.

Ioannis