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Bar Code Knowledge Base

The Barcode-Store.com Knowledge Base is a growing inventory of information and answers to Frequently Asked Questions on bar code related topics. If you have bar code related questions that aren't answered here, or if you'd like to suggest an addition to this section, please feel free to give us a call.

Cable Interfaces

One of the most common questions we get is regarding different cable interfaces. Here are the most popular types.

PS2 interface USB interface Parallel interface RS232 interface Serial interface

Data Collection: Glossary of Terms


Labels: Frequently Asked Questions

QUESTION:
I've heard the phrase "two up" used. What does that mean?
ANSWER:
It refers to the number of labels across the width of the roll.
EXAMPLE:

ONE UP
TWO UP
THREE UP

QUESTION:
When you describe a label size (ie., "4x6"), which number
represents the height, and which number represents the depth?
ANSWER:
The first number (the "4") represents the height,
and the second number (the "6") represents the depth.
EXAMPLE:

QUESTION:
What is the standard spacing between labels when they are still on the roll,
and what does the "core size" mean?
ANSWER:
The standard spacing between labels when they are still on the roll is 1/8th of an inch,
and the "core size" refers to the diameter of the roll on which the labels are wound.
EXAMPLE:

QUESTION:
What are "Direct Thermal" labels?
ANSWER:
Direct Thermal labels are printed on a material that reacts to the heated impact of a direct thermal imaging device. The label has a special coating that turns black when the heated pins of the thermal printer strike it, leaving a mark on the paper. Several different coatings are available. It is important to match the coating to the imprinting device for optimum performance. Our sales force will be happy to assist you in your selection of the appropriate materials for your machine.

QUESTION:
Does the use of "Direct Thermal" labels have any effect on the life of
my bar code printer's print head?
ANSWER:
Yes. With the Thermal Direct method, the print head is in "direct" contact with heat sensitive paper (i.e. labels), and no ribbon is used. As a result, consumable costs are lower (i.e. no ribbon is consumed), but the print head undergoes SUBSTANTIALLY MORE wear and tear. The smooth wax-resin ribbon produces far less friction than paper, so a print head lasts approximately FOUR TIMES LONGER when printing in Thermal Transfer mode versus Direct Thermal mode. Print heads should be and are considered consumable items - and they add considerably to the overall cost of producing a label.
QUESTION:
What are "Thermal Transfer" labels and how are they different from "Direct Thermal" labels?
ANSWER:
Thermal Transfer labels (or indirect thermal) are similar to Direct Thermal labels except for the coating of the material. Thermal Transfer products rely on a coated ribbon in the printer to create the black markings. Thermal Transfer ribbons are available in several different technologies. They can be resin, hard wax, soft wax or other configurations. As in Direct Thermal, the match of ribbon/label material is important to performance. Consultation with our sales force will assure the correct product mix to achieve the combination of quality image and best value/lowest price to serve your needs. 

Bar Codes: Frequently Asked Questions

What is a Bar Code?

Bar code is a pattern of bars and spaces which represent numbers, letters or characters.

Code 39, for instance, has a unique pattern. Code 3 of 9, as it is sometimes called, derives its name from the way in which the pattern is created. Each character has nine elements (five bars and four spaces) and three of them are fat.

Why Use Bar Code?

Bar codes are accurate. They eliminate manual data entry errors. Research has shown that the error rate due to bar code misreads is less than one thousandth of one percent. Tests have shown that bar coded information had a throughput accuracy rate of 1 error in 10,000,000 characters. Compare that to keyboard entry error rates of 1 error in 100 characters.

Bar codes speed data entry. Even with a simple wand, a bar code can be scanned in a fraction of the time it takes to enter the information manually. CCD and laser scanners are also available for even faster data entry.

Bar codes can be produced easily and cheaply. Bar codes can be printed on most computer printers, for the cost of ink and paper. Even a low cost dot matrix printer can produce bar codes of adequate quality.

How Does a Scanner Work?

Scanners are the devices that read bar codes. A scanner shoots pulses of light. If it falls on a light area, a zero (0) is read. If it falls on a dark area, it reads a one (1). Scanning the bar code generates a string of zeros and ones. This pattern of zeros and ones represents the characters encoded. The scanner software, or firmware, translates or decodes the strings into characters.

The scanner must be able to shoot a straight line across the bars and spaces. The taller the bars the greater the angle and the greater the chances of getting a good reading.

The shorter the bars the less likely the scanner will be able to shoot a straight line through the bars and spaces.

What Does the Bar Code Represent?

No matter which bar code is used, the information encoded in the bars and spaces may be displayed above or below the bars. Since this is the aspect understandable to us, the characters are referred to as human readables. The bars and spaces are readable by machine.

UPC (A) is just one of several bar code symbologies. In the typical format, each of the elements of the bar code symbol represent predefined information.

The system digit and the manufacturer number are assigned by the Uniform Code Council, Inc. for UPC (Universal Product Code) in the United States and Canada. UPC is a subset of EAN (European Article Number), the international product code standard throughout the rest of the world.

The product identification number is assigned by the manufacturer. The check digit is used to check the data that is read.

These are, perhaps, the most commonly used bar codes. They can be found on almost all general merchandise.

There are over 24 bar code symbologies, but only about 5 are in common usage. Having said that, someone will dispute my number. Other than the ones listed below, there are 5-7 new symbologies that are attempting to replace the ones in use today. These new codes are good symbologies and will take their place in the ADC world, but it will take some time for them to become common in usage. These are the 2 and 3 dimensional symbologies that are being used for specific applications in the courier and transportation industries.

UPC - As of today is the bar code you see in the grocery and retail stores. It is only used for POS in retail applications. The UPC bar code consists of 4 parts. The 1st number is the system identifier; next 5 digits are the manufacturers assigned number; next 5 digits are the manufacturer's own assigned product number and the last digit is the check digit.

UCC/EAN- Code 128 symbology is used to identify products on shipping containers. There is a standard format for shipping container labels. The shipping Container Code also uses Code I 2/5 symbology for printing on corrugated containers.

Code 39 or Code 3 of 9 is the most common symbology for printing bar codes for other uses than retail. It, and Code 128 are both alpha/numeric and very flexible.

Codabar is still used by most libraries today but some are changing to C39. This is due to history rather than design. Codabar was the first symbology to be used by any group and libraries started using bar codes before the retail industry.

The manufacturer's assigned number has to be issued from;


  1. The Uniform Code Council in the USA
    202 - 1009 Lenox Drive, Lawrenceville, New Jersey, 08648 
           phone: (609) 620-0200  fax: (609) 620-1200 website: http://www.uc-council.org
  2. Product Code Council of Canada
    1500 Don Mills Road, Suite 800,Toronto, Ontario, M3B 3L1
    phone (800) 567-7084, fax (416) 510-1916 website: http://www.gs1ca.org/home.asp
The assigned number is for use anywhere in North America

Elements of Bar Code

No matter which symbology you will be using, all bar code share elements that make up the symbol. These are the bars and spaces, the human readables, and the quiet zone. In addition, a symbology may be either Discrete or Continuous.

Bars and Spaces

The bars and spaces determine the pattern of the encoded data. Each symbology represents a different strategy behind the creation of these patterns such as: being as condense as possible, printing as easily as possible, being as easy to decipher as quickly as possible, etc.

Each bar code has slightly different quiet zone requirements. For example, the quiet zone of Code 39 is ten times the width of the thinnest bar/space or 0.25 inches, whichever is greater.

Human-Readables

The human-readable is the data represented by the bars and spaces printed as text for people to read. The actual data encoded here is 3*35353*2. The asterisks are not displayed as human-readables in this example.

The Quiet Zone

The quiet zone is the clear area (free from marks) before and after the bars and spaces. Having a quiet zone is as important to readability as the bars and spaces! Scanners need to establish values for the quiet zone before they can evaluate the bars and spaces. Reading the color and reflectance of the quiet zone establishes how the spaces will read and determines the difference between the spaces and the bars. Bar code cannot be read without a quiet zone.

Even though the quiet zone actually surrounds the code (the Bar/Space image), the clear area above and the below the Bar/Space image is not required for readability of most symbologies.

Discrete vs. Continuous bar code

Discrete symbologies consist of unique bar and space patterns for each character. Continuous codes cannot be separated into individual characters.

ITF is a continuous bar code. You cannot pull it apart into discrete, individual characters. Notice how the bars of the 3 and 5 are embedded in the bars of the 8 and 2.

Codabar is a discrete bar code. You can pull apart characters into discrete, individual units. The spaces between characters do not have critical dimensions.

The pattern of the number five is 310000102 where å11 is a wide bar or space and å01 is a narrow bar or space.

What is a Check Digit?

A check digit is used to check that the data is read correctly. Different symbologies apply different formulas to the encoded numbers to yield a single digit. That digit is the check digit. That check digit is usually added to the end of the already encoded numbers.

The computer checks that the numbers were read correctly by comparing the check digit it calculates against the check digit it read.

For example: When encoding the ZIP code 311215-12352 into POSTNET, the check digit is the total of the numbers subtracted from the next higher multiple of ten. 1 + 1 + 2 + 1 + 5 + 1 + 2 + 3 + 5 = 21 30 is the next higher multiple of ten 30 - 21 = 9 the check digit = 9

In the POSTNET bar code the numbers to be encoded would be 311215123592. The bar code reader reads 311215123592. Reading a check digit of 392 and calculating a check digit of 392 from the other numbers it read, the bar code reader now is doubly certain that the numbers were correctly decoded.

Bar code technology is millions of times more accurate than typing when it comes to entering information into the computer. Check digits make the systems even more accurate. Tests have shown that operators may do 10,000,000 entries between errors when using check digits.

How Small Can I Make the Bar Code?

How small the bar code can be becomes a function of how finely the printer can print and how fine of a bar code a reader can read.

Industry guidelines will strongly caution against undersizing bar codes. This is good advice. There may be times when you want bar code as small as possible, however, this is only true until it becomes less readable. You must then weigh the difficulties that may be encountered when reading the bar code against the advantages of having smaller bar code.

UPC, EAN and JAN codes should never be used below 80% magnification. Even then this should be done only when the printing techniques are controlled and of sufficient resolution to get the tolerances necessary.

UPC, EAN and JAN codes should never be used below 80% magnification.

All of your work should be verified, especially at lower (smaller) magnifications.

Readability vs scannabilty

Readability is the measurement of how well the symbol is interpreted. scannabilty is a measure of the ease with which the scanner can decipher the symbol. For example, if two symbols were equally readable, a tall symbol is considered more scannable than a short one because there is a greater chance that the scanner will see the taller symbol.

Likewise, two symbols that are equally scannable may differ in readability due to the narrowness of the symbols or the quality of the printing.

The specifications that affect the readability and scannabilty of a symbol are width, color, printer dpi, bar width reduction, reflectance, and contrast. Symbol height only affects scannabilty.

In relation to retail checkout counters, first-scan readability is the ideal. In other words, the goal is for the scanner to be able to read the symbol the first time it is scanned. It does no good to create bar code that causes the checker to have to try over and over to read it. After a while the checker will stop attempting to scan your products. Worse yet, your products may be pulled from the shelves and returned to you if they don't scan easily. The goal is for the scanner to be able to read the symbol the first time it is scanned.