I have been trying to collect enough 8510 modules for a system. Among other items I have: 85101C, 85102A, 8515A, 83631, 2-large D-Sub interconnect cables. Is possible to operate the 85101C with the 85101A? If so what functionality is lost? What is the difference between the 85102 A and B? Can My A be modified to a B without an (I'm sure obsolete) upgrade kit?