a transponder that may be used as an rfid tag includes a passive circuit to eliminate the need for an “ always on ” active rf receiving element to anticipate a wake - up signal for the balance of the transponder electronics . this solution allows the entire active transponder to have all circuit elements in a sleep state , thus drastically extending battery life or other charge storage device life . also , a wake - up solution that reduces total energy consumption of an active transponder system by allowing all non - addressed transponders to remain in a sleep state , thereby reducing total system or collection energy . also , the transponder and wake - up solution are employed in an asset tracking system .