Patent ID: 7274284

Claim:
A method for identifying any RF cards in an RF card reader's field, the method comprising: a) sending a command from a group of commands including: i) a first polling command requesting a response from any card in the field in an Anticollision state, said first polling command also moving any card in a Halted state to the Anticollision state; ii) a second polling command requesting a response from any card in the field in the Anticollision state; and iii) a third polling command requesting a response from any card in the field in the Anticollision state which has chosen a particular timeslot in which to respond; b) where a clear response from the sent command is received from a responding card: i) saving the response; ii) moving the responding card to an Active state; iii) incrementing a timeslot number and, if the incremented timeslot number exceeds a predetermined maximum number of timeslots, moving to step d), otherwise repeating steps a) and b) until no clear response is received; c) where no clear response is received from a responding card, determining whether a collision occurred and, if so, repeating steps a) and b) until no clear response is received, and if no collision occurred, moving to step biii); d) returning a value indicating a number of responding cards.