A smart dimmer switch for control of a lighting load from an AC voltage source can replace any switch in a three-way or four-way lighting control system. The smart dimmer switch can be connected on the line-side or the load-side of a three-way system with a standard three-way switch in the other location....http://www.google.co.uk/patents/US7830042?utm_source=gb-gplus-sharePatent US7830042 - Dimmer switch for use with lighting circuits having three-way switches
