Abstract: The communication protocol between at least one transceiver unit (communication unit) and transponders or transceivers (transponders) associated with said unit is characterised in that at least one initial command is sent by said unit to generate interaction with said transponders entering its field of action, said initial command having at least partially a coding with a specific time structure which is different from the basic time structure used for encoding said coded data. The specific time structure has greater coding time periods than the coding time periods of the basic time structure. At least one coding period of the specific time structure has a constant characteristic electric value over a time interval greater than the duration of said constant characteristic electric value able to appear in any bit sequence having the basic time structure.

Abstract: The electronic memory (2) includes blocks (M1 to MN) associated respectively with protective sequences (P1 to PN) and decision units (D1 to DN) which control access to the memory blocks. The protective sequences include at least two bits. In order to protect the memory blocks against physical actions which could vary the inscribed code, access to a block is closed when the corresponding protective sequence has identical logical states.

Abstract: The compact disk comprise a data storage medium (2) for optical reading situated in an annular region (4), which defines a central region (6) wherein is arranged an electronic module, formed of an electronic unit (12), in particular an integrated circuit, and an antenna formed by a winding (14), made of an electrically conductive material. The electronic module allows contactless electromagnetic coupling with an electromagnetic wave transmitter-receiver able to communicate with said electronic unit. In particular, this electronic unit comprises an identification code and/or a decoding key for the data contained in said storage medium.

Abstract: An object identification system comprises a transceiver (1) and a transponder (30) including memories (33,34) for storing an identification code identifying the transponder. Circuits (35, 36, 37, 38) generate an identification signal representative of the identification code such that the identification signal is modulated by bits of the identification code. Circuits (8, 9, 10, 11, 12) of the transceiver receive and interpret the identification signal. The transponder includes a variable code generator (32) and a controller (31) for controlling the writing of the variable code into memory (33) so that the variable code constitutes part of the identification code. The variable code may be a random or pseudo-random code.