The "normal" key card lock system is battery powered ... I've been in several hotels with complete electrical failures -- even the emergency generators failed -- and the card locks were just about the only thing that kept going (even the emergency lights in the stairways were dark!). Wonder what system the 4PTs in SYD uses? I've stayed there and didn't notice anything special about the lock that made it look different from the normal battery operated system (but I was less interested in the doorlock than the view from my surprisingly lavish suite there).