Abstract: A method of selectively addressing one or more transponders in a set (17) of transponders (21, 22, 23, 24, 25) is described. The method comprise transmitting a first set of one or more commands (25; 251, 252) selected to be not executable by a first subset (24; 242) of transponders or to be executable in a shorter time by the first subset of transponders than by a second subset of transponders (23; 231, 232) in the set, and transmitting a second set of one or more commands (26; 253) such that the second set of commands are received by the transponders while the second subset of transponders are still executing the first set of commands.

Abstract: Ancillary data (51) can be used to reduce collisions and/or speed up authentication when inventorying transponders. A method is described which comprises retrieving 5 ancillary data for a set of one or more transponders (4), the ancillary data comprising characteristic data other than a permanent identifier and generating one or more commands (54) addressed to a set of one or more transponders in dependence upon said ancillary data. A method for creating ancillary data is described. The method comprises receiving inventorying data resulting from 10 inventorying one or more transponders, each transponder having at least one permanent identifier, extracting ancillary data from said inventorying data and/or generating ancillary data in dependence on said inventorying data.

Abstract: Selectively addressing transponders A method of selectively addressing one or more transponders in a set (17) of transponders (21, 22, 23, 24, 25) is described. The method comprise transmitting a first set of one or more commands (25; 251, 252) selected to be not executable by a first subset (24; 242) of transponders or to be executable in a shorter time by the first subset of transponders than by a second subset of transponders (23; 231, 232) in the set, and transmitting a second set of one or more commands (26; 253) such that the second set of commands are received by the transponders while the second subset of transponders are still executing the first set of commands.

Abstract: A method of tracking an object (1) tagged with a radio frequency identification tag (2) having an identification code using a network of readers (3) is described. A reader (3) interrogates the tag (2) by transmitting its identification code. In response to receiving its identification code, the tag identifies itself to the reader. Otherwise, it does not identify itself. The method comprises identifying an expected location of the object and directing one or more selected readers according to the expected location to interrogate the tag using its identification code.

Abstract: A method of tracking an object (1) tagged with a radio frequency identification tag (2) having an identification code using a network of readers (3) is described. A reader (3) interrogates the tag (2) by transmitting its identification code. In response to receiving its identification code, the tag identifies itself to the reader. Otherwise, it does not identify itself. The method comprises identifying an expected location of the object and directing one or more selected readers according to the expected location to interrogate the tag using its identification code.