Abstract: In a contactless electronic tag identification system including a multiplicity of electronic tags associated with a query/read/write device, the electronic tags transmitting messages at instants selected randomly or pseudorandomly during an interval of time or beat, a process for detecting in the query/read/write device substantially simultaneous transmission of at least two electronic tags, including (a) transmitting at a beginning portion of each electronic tag message a signal sequence selected from a set of sequences, (b) recognizing upon receiving messages by the query/read/write device the received signal sequence at the beginning of each message, and (c) detecting substantially simultaneous transmission of at least two electronic tags if the recognized signal sequence does not correspond to one of the sequences of the set.