PXT® Probe communicates with its key information sources (PXT® Portal and PXT® Transponder) via Bluetooth® technology, leveraging the same basic technology underlying the operation of wireless headsets for mobile phones. PXT Probe and PXT Portal run on Windows Mobile® smartphones and PDAs and use the built-in Bluetooth chipset and the native Microsoft Bluetooth stack. The PXT Transponder has a functionally equivalent chipset and software stack embedded at the heart of its communication infrastructure.

The simple, inexpensive, and reliable method of low-power limited-distance communication afforded by Bluetooth technology is ideally suited for proximity-based information systems.

The PXT Probe and its information sources can communicate in a many-to-many fashion; that is one PXT Probe can communicate with many PXT Portals and PXT Transponders, each of which can in turn communicate with many PXT Probes. The key to communication is proximity: the PXT Probe and its information sources can communicate whenever they are within 10m of each other, the approximate Bluetooth Class 2 distance limitation. Communication possibilities are illustrated below.

The illustration represents two information consumers equipped with PXT Probe software (P1 and P2), each with a view range of 10m in all directions. As shown user P1 is able to communicate with 6 transponders because that many are positioned within a radius of 10m. User P2 is able to communicate with 3 transponders. Both users have access to transponder T10.

Looking at it from the perspective of the transponders (the information suppliers), we see that each can communicate with only one user with the exception of T10, which can communicate with 2 users (P1 and P2).

Of course these associations will change as P1 and P2 move about.

Take an art museum to consider the practical effects of this communication model. One museumgoer can access information about several different paintings that are nearby (i.e., <= 10m), and the transponder associated with any one of those paintings can also serve any and all other museumgoers who are within 10m.

As the user moves about within the museum, different objects (e.g., paintings) will come in and out of view, depending on their proximity.

At the same time the fixed-position transponder serves a succession of users as they come within range and issue information requests.

The same basic model applies regardless of whether the information source is a PXT Portal or a PXT Transponder. The only difference is that PXT Portal is mobile, not fixed-position like PXT Transponder.

The beauty of the proximity-based approach - from the user perspective - is that the information is always available on-the-spot, when you need it, where you need it.