Thanks Buzz, I went through the manual I found and all it really says is that if a 603 is added then the 600 has to be above a certain software version and then the 603 can be added to the 600 software. What I don’t see is that specific programming and if it’s for any 603 set the way you put it in programming or if it’s specific to that piece of equipment due to MAC address or other. My thought is that the 603 is dumb and the 600 does all the work therefore as long as the dip switches line up then it should be a direct swap and the 600 won’t know the difference. Hopefully somebody can tell me if that assumption is correct.