It's a ZigBee radio that sends check-ins every so often to a hub/router. If hub hears messages then the tag is there, if there are no messages after a certain amount of time then the tag is gone.
It's a ZigBee radio that sends check-ins every so often to a hub/router. If hub hears messages then the tag is there, if there are no messages after a certain amount of time then the tag is gone.