I'm switching from a Maple Chase 9610 thermostat to a Honeywell RTH7600D. The thermostat attaches to an EWC Zone controller. The zone controller and the 9610 have separate O and B terminals. The 7600D only has an O/B terminal. The system is a conventional Heat (Gas)/AC. I'm looking at how my wiring needs to be in the 7600D to compensate for the separate O and B terminals. The system has 3 zones with the 7600D connected to the Main, Zone 1. The old Maple Chase was wired to the EWC-> RH/RC to R1, Y to Y, W to W, O to O, B to B, G to G. The other two zones are simple 3 wire so no issues there.