US Patent 8451088 Electronic lock box with transponder based communications

An electronic lock box contains a secure compartment for storing dwelling keys to a structure, and is typically mounted outside the dwelling structure. When properly instructed, usually with a coded message, the dwelling key can be accessed by opening the door to the secure compartment; such message can be manually entered on a keypad, or a programmed electronic key device can make the process more automatic. A lock box system uses a transponder at a dwelling base station (typically within the dwelling structure) to relay lock box status or access event information over a short range radio from the lock box to a remote central computer by using a more traditional communication system that is available within the dwelling. Additional sensors can be used to monitor the status of vandalism attempts. Furthermore, the lock box/transponder communications may be programmed so as to allow detection if the lock box is stolen.