Patent ID: 8643472

Claim:
A method, comprising: receiving by a transponder an unmodulated carrier signal from a base station; transmitting a first locating signal in response to the transponder moving within range of a communication zone of the base station based on a field strength of the received carrier signal, the first locating signal generated through phase modulation and backscattering of the received unmodulated carrier signal sent by the base station; discontinuing, in response to receiving a first selection command, transmission of the first locating signal; receiving by the transponder a locating command; transmitting by the transponder, in a persistent operating state, a second locating signal, the persistent operating state allowing the transponder to receive a switch-off command while simultaneously transmitting, without an interruption for receiving the switch-off command, the second locating signal; and discontinuing transmission of the second locating signal, in response to one or more of: receiving the switch-off command; or an expiration of a pre-determined period of time.