RFID (radio frequency identification tags) could possibly replace UPC barcodes. They are radio frequency devices like those in library books and CD and DV packaging, but they contain a 96-bit serial number. This system is called the EPC, or electronic product code.
This page currently houses resources for learning more about barcodes and assignments for the Advanced Topics course.
Examples:
Postnet:
UPC
MaxiCode
PDF417
RFID:
The mathematics of error detection and correction are essential for understanding the structure of all types of barcodes
All 1D barcodes use a check digit to help scanners detect and (sometimes) correct read errors
The Postnet barcode, used by the USPS, has the simplest type of check digit. Postnet encodes the 9-digit zip code (sometimes along with 2 walk sequence digits) into tall and short bars, but adds a check digit at the end to ensure that all the digits add up to a multiple of 10 (or are equal to 0 mod 10).
Although all other 1D barcodes use a check digit (as do credit cards, airline tickets, and bank checks), the check digit schemes for these vary widely and involve not just addition of digits but complicated schemes of multiplication.
All 2D barcodes (or symbologies) have ways of detecting and correcting errors also, but they include several, even sometimes hundreds of check bits in the symbol.
In the Advanced Topics course, we cover the structure of several 1D and 2D barcodes and analyze (to some extent) the check digit schemes for each. We also look at RFID (radio frequency identification), which is a remote, wireless form of a barcode. This technology is expected to replace traditional barcodes in the next decade or so.
RSA Inc., which is the company behind the strongest form of prime number encryption, is now directly involved with RFID, providing systems that will add security to the use of RFID tags.
POSTNET Barcodes
Postnet is the system used by the U.S. Post Office to encode zipcode information onto an envelope.
An Optical Character Recognition (OCR) machine reads the ZIPCode and address on each envelope and calculates a 10- or 12-digit number that gets converted to a barcode
The barcode converts the following digits....
Digits 1-9: The regular ZIP+4 numbers
Digits 10/11: WalkSequence Digits (helps automated sorters put mail in order of delivery)
Digit 12: The Check Digits (chosen so that all 12 digits add to a multiple of 10)
...into a series of tall and short bars using the following system: TALL BAR = 1, SHORT BAR = 0
Each digit is assigned 5 bars, where the place values are 7/4/2/1/0 and that 11000 = 0
This would result in the following table:
In addition, a "start bar" and an "end bar" (sometimes called "frame bars") are added to the beginning and ending of each code to indicate the reader to start and stop reading the code (these are tall bars).
EXAMPLE:
Notice the tall bars at the start and end.
See if you can figure out the digits of the ZIPCode based on these bars....
Here is more material that I have prepared for teaching my class:
1D BarCode Check Digit Schemes:
First, a definition: “x mod n” = the remainder upon dividing x by n
examples: 13 mod 5 = 3 (13/5 = 2 with remainder 3)
7 mod 2 = 1 (7/2 = 3 with remainder 1)
4 mod 10 = 4 (4/10 = 0 with remainder 4)
Now, The CHECK DIGIT SCHEMES:
(c = the check digit) Postnet: ZIP + 4 = 9 digits + 2 Walk Sequence digits = 11 digits (not incl. check digit)
c chosen so that:
(z1 + z2 + z3 + z4 + z5 + z6 + z7 + z8 + z9 + w1 + w2 + c) mod 10 = 0
UPC: Product type digit + 5-digit manufacturer number + 5-digt product number = 11 digits (not including check digit)
c chosen so that:
[3(d1 + d3 + d5 + d7 + d9 + d11) + (d2 + d4 + d6 + d8 + d10) + c] mod 10 = 0
ISBN:11-digit scheme similar to UPC
starting after “978”: c chosen so that:
(10d1 + 9d2 + 8d3 + 7d4 + 6d5 + 5d6 + 4d7 + 3d8 + 2d9 + 1d10 + c) mod 10 = 0
Airline Tickets:10-digit number
c chosen so that:
(d1+d2+d3+d4+d5+d6+d7+d8+d9+d10+d11+c) mod 7 = 0
Bank Account: 10-digit number
c chosen so that:
[7d1 + 3d2 + 1d3 + 7d4 + 3d5 + 1d6 + 7d7 + 3d8 + 1d9 + 7d10 + c] mod 10 = 0
2D Symbologies: Uses, Types, Capabilities
Organizations that have adopted 2D Symbologies:
EIA - Electronics Industry Association
AIAG - Automobile Industry Action Group
SEMI - Semiconductor Equipment & Materials International
DOD - U.S. Department of Defense (adopted PDF417 for military ID cards)
TCIF - Telecommunications Industry Forum
...others
Actual Uses of 2D Symbologies: Medical:
• Unit-dose packages in the hospital industry
• Blood bank identification
• “Specimen” tracking
• Identification of laboratory glassware and laundry marking
Industry:
• Direct-mail reply cards (company can scan reply card quickly for name, address, and demographic
information instead of looking up name in database of millions)
• Recycling industry - encode contents of large containers for sorting
• Labeling small computer chips and PCBs (printed circuit boards in computers) for
tracking purposes in factories and beyond
• Sorting packages
• Hazardous materials tracking
Other:
• ID card information/driver’s licenses
• Encoding fingerprints
• Encode equipment calibration instructions
Capabilities:
some can:
...pack 500,000,000 characters per inch
...be read at distances of up to 125 feet
...be merged with the design of the product they are printed on
...add encryption to the data
...encode images, video, audio, executable files
all:
...eliminate time-consuming and error-prone manual data entry
...can add the data to labels that are already being printed for an object
