Original Publication Date: 2002-Nov-22
Included in the Prior Art Database: 2003-Jun-21
Portable devices are an immerging technology for use in the retail store applications. Applications for location prompted advertisements, position specific product location directions and location data mining create the need for a inexpensive location system that is compatible with other technology in the store. Disclosed here is a system that can locate portable devices to within a foot or less if stationary and within a couple of feet if moving. This system requires that the portable device contain a microphone, an internal clock, computing capability and wireless communicationswhich are already present on most known portable tablet devices. Also required are at least two high frequency speakers that are driven (wired or wireless) by a computer. Installation is simply and inexpensive and the portable devices are standard. Figure 1 shows the Ultrasonic Locator. The frame indicates the walls of a retail space. Speakers A and B are fixed to the corners of one wall and at the ceiling. Additional speakers can be added to handle different shaped spaces. These speakers emit a high frequency tone (~40,000 Hz.) for a short time (~25 msec.). This will be referred to as a "beep". This tone is above the hearing range of the customer and should not interfere with the customer or other equipment in the store. Shown are Portable Devices, 1 and 2. There is no limit to the number of portable devices that can be located at a single time. Prior to a location sequence, the Ultrasonic Locator controller clock and the Portable Device clocks are synchronized. Although this can be done in various ways, this embodiment will require the wireless communication link to periodically send out a synchronizing signal to all portable devices in the space. Clock synchronizing and clock stability are key to accurately locating the Portable Devices. A clock error correction factor may need to be used in calculating the distance from the speakers. This correction factor is determined by recording the time adjustment required to synchronize the Controller clock and the Portable Device clock and dividing that adjustment by the time since that last synchronization. This factor, when multiplied by the time inteval, is used to calculate the distance and should correct for nearly all of the variations between the two clocks.