RS didn't have any, so I bought a null modem adapter instead (and saved $20). I tried it with the null and it didn't work. I thought I was stuck. BUT then in desperation, I tried it with my previous cable setup without null. Viola! it worked.
Any mac people reading this-- I have Soft AT, a great program that makes my great mac into a great 286. (I don't think that this is a real in-demand product.)
Good luck to other mac people.
Matt.
Sorry about length.