Can you please explain how tag-reader interaction works?
Dear K. Manochitra,
Active tags communicate in one of two ways. Either a tag remains asleep until coming within range of a reader, at which point the reader sends a signal to wake it up, or the tag beacons. For real-time location systems, the tag emits a signal every 5 seconds, 10 seconds, 1 minute or whatever span of time a user desires (beaconing more often provides more real-time information, but uses up the battery more quickly). The protocols used in active systems vary, as does the means of determining location. The most common way to determine location is to triangulate on a signal with three antennas recording the time of arrival, and then use software to pinpoint the tag's location.
—Mark Roberti, Founder and Editor, RFID Journal