Guys, thanks for the replies. Yes, I agree their RS232 reference is a little misleading and could confuse a beginner. I will be using a PIC to drive the unit so TTL is actually what I am looking for.
I was trying to replace a Lantronix XP1001001-04R (which is no longer made). I'm guessing the XP1002000-05R replaced the 04 unit. I do not need multiple connections as it will be a one way transmission from one endpoint to another.
One thing I am concerned with is the fact that the USR-K1 and USR-K2 apparently do not come with an embedded MAC address. Apparently only the USR-K3 has the MAC address. It is about double the cost of the K1 unit but still less money than the Lantronix unit by a long ways.
Has anyone actually used one of the units? If so, how difficult is the setup? If I am reading and interpreting the data notes correctly, only the K3 has a web setup page. The other two have to be setup using AT commands.