The printer must isolate the individual tag to which it is writing during the print process. For this reason, RFID printers have integrated a very low power reader with an antenna designed to read tags that are in close proximity. This requires proper alignment of the RFID tag within the label and within the print pad.
Tip: Know that writing to a tag requires more time and power than reading from a tag, so this means that a writing application will be a lot slower than simply reading the tag and applying it to the box.
The following sequence of events takes place to print and encode a label:
- The printer receives a command and data from the host computer.
- The label is positioned so that the reader can check for null data on the tag. Null data is placed in a tag by the tag manufacturer to indicate that the tag has passed the manufacturer’s quality control. A quiet tag that was pre-identified at the manufacturer will not have null data written; therefore, this tag will be automatically rejected. The printer does not attempt to program this tag and does not self-test the tag for any signal strength but simply rejects it.
- If the tag passes a validity check, the printer will write data to the tag and then verify the data it has just written.
- If the verification fails or the tag does not respond with the appropriate signal strength, the tag is marked with a special void mark; it is then rejected, and the process is repeated on the next label.
- Once the tag is successfully encoded, the barcode and other information is printed onto the label and an acknowledgement is sent back to the host. This acknowledgement contains the serial number that was just written to the RFID tag, as well a successful print signal.
- The printed and encoded label is now presented to the user for application to the package.