Patent ID: 8604909

Claim:
A system for determining a location and an identity of a portable device, the system comprising: means for transmitting timing synchronization information including a plurality of RF transceivers coupled to a backbone network and a time server generating the timing synchronization information; wherein each of the plurality of RF transceivers periodically transmits a request to the time server to receive the timing synchronization information; a plurality of stationary ultrasonic base stations, each ultrasonic base station configured to receive the timing synchronization information and to transmit a corresponding ultrasonic location code in a time period based on the received timing synchronization information, each ultrasonic location code representative of a location of the respective ultrasonic base station; and a plurality of portable devices, each portable device configured to 1) receive the timing synchronization information, 2) detect the ultrasonic location codes from the ultrasonic base stations and 3) transmit an output signal including a portable device ID representative of the portable device and the detected location code, wherein each portable device is synchronized to detect the ultrasonic location code in the time period based on the received timing synchronization information.