door plate 12 is mounted to a surface 24 of wall 6 within guest room 8 preferably near a door 26 to the guest room 8 external door plate 14 is mounted to a surface 32 of wall 6 external to the guest room 8 preferably near the door 26 power is supplied to the internal door plate 12 from power supply device 16 which may comprise any u l or other appropriately approved device that can receive 100 240 vac 50 60 hz line voltage inputs and deliver for example 300 ma of 12 vdc output power supply device 16 may be mounted in any location at which it can tap into line voltage wiring 18 and from which low voltage wires 20 can be run to the internal door plate 12 an entry door switch 100 is optionally coupled to door plate 12 via line 110 for communicating an open or closed door condition to door plate 12 entry door switch 100 is preferably located proximate door 26 on wall 6 a mechanical or magnet contact 111 may be disposed on door 26 to provide operable communication of door 26 in an open or closed condition to switch 100 referring to fig2 through 5 various views of the.