Hey! I was happy to be designing this beauty (and using it everyday in our office). It's nothing more than just a "stair switch" configuration, where one of the manual switches was substituted with a relay. So we have all SPDT manual switches on the walls, and SPDT relays connected with them in our control cabinet. Every switch/relay can change state of the receiver (in this case a LED lamp) at any time. So even if relays or RPIs fail we can still be using manual switches. More info here https://goo.gl/sJw9F1 .