Patent ID: 6354500
Filing Date: 2002-03-12
Classification: G06K

Abstract:
A method for communicating with a plurality of contactless data carriers, comprising:a base station transmitting a power signal; a data carrier powering itself up in response to the transmitted power signal, and entering a wait state; the base station transmitting a first start up signal for waiting data carriers; the waiting data carriers exiting the wait state in response to the wake up signal and transmitting identity information in a time slot that is randomly self-assigned; the base station registering the identity information by polling the registered data carriers and initiating dialogue with registered data carriers in an order determined by the random self-assigned time slots of the registered data carriers; the base station completing dialogue with a first registered data carrier; the first registered data carrier shutting down for a remaining time of a communication session; the base station transmitting a second start up signal to initiate dialogue with a next registered data carrier, the base station initiating dialogue with all of the registered data carriers to complete the communication session; and wherein the first and second start up signals are distinguishable, the first start up signal being used to initiate a communication session with any one of the data carriers, the second start up signal being used to continue the communication session with only registered data carriers.