RFID = Radio Frequency Identification
By bringing a card or tag close to a reader the reader sends a pulse of engery which the RFID chip uses to power itself just long enough to send back a tiny amount of information stored it - such as its serial number.
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Leave a card or tag on the reader and write down the ID# that shows up on the screen.
You must include the X (capital) and any other characters exactly as you see them:
Such as - 0 .
You will need the modified (hacked) firmware that uses Read Analog 8 to return the RFID ID#.