Scott,
The problem it that there are no IR codes for different house codes (A-P), only unit codes(1-16)! If you used one IR543 in the bedroom on housecode A and one in the living room on housecode B, you would be fine. The problem is if you were to use more than 1 IR543 in one location. Both IR543's would transmit at the same time and cause a collision of signals. This in turn would lead to nothing being completed.

Hope this helps,
Chris Couture