The CM15A remembers the state of modules that it controls. There are drawbacks to that. For instance, I have some WS13A wall switches in my house. If I go and manually turn them on at the switch, the CM15A doesn't know that I did that because the WS13A didn't transmit a signal to it telling it that I activated it. However, if I use AHP to activate it, the CM15A is what is turning it on or off and remembers it. The same goes for an RF remote. Since the RF remote runs through the CM15A, it can remember the state.
Hope that all makes sense
Dan B.