RFID reader sends an encoded radio signal for interrogating the tag. The RFID tag gets the message and then reacts with its identification and other information. This may be an exclusive serial number, or may be such information that is related to the product. For example a stock number, batch or lot number, date of production date, or other specific information is given.
As tags have specific serial numbers, the RFID system design can distinguish several tags. They might exist in the range of the RFID reader and read them at the same time. To get more information on this subject, it is suggested to perform a research on the Internet with the keyword RFID chip timing Newton Massachusetts.