Only active tags are automatically pinged by the system.
I can't agree with that, Roger (but maybe I was causing confusion by using the words "automatically pinged").
Surely passive tags
do have to be interrogated by a reader in order to give up (return) their information. Passive tags are often embedded in "stores" items, such as linen in the laundry, and trays (
etc.) in CSSD. But they only respond when asked ("pinged").
Meanwhile,
active tags fall broadly into two types:- transponders and beacons.
For active transponder tags, as with passive tags, the reader will send a signal first, and if it's within range the active tag will reply with the information it holds. Transponder tags conserve battery life when the tag is out of range of the reader. In other words, like passive tags they (also) only respond when asked ("pinged").
With active beacon tags, the tag does not wait for the reader’s signal, but instead broadcasts its information every few seconds or so. Obviously beacon tags are useful when tracking portable equipment (especially when on the move). A compromise needs to be made to balance range (can be hundreds of metres) with battery life, but they carry on responding even when not explicitly asked (or "pinged"). The only question then remains whether or not any reader is within range to pick up the signal.
But how does a tag know of any type know where it is (in order to report its location)? There must be some sort of "triangulation" (similar to radio direction finding) going on. In other words, the tag does not know ... its the readers (acting collectively when in range) that "work out" a tag's location and log it in a database.
