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All about Barcodes


From an original idea patented in the USA in 1952 by [Woodland and Silver], barcode really became commercialised in the late 1960s in the USA, driven by two key industries, the Grocery/Food/Supermarket sector and the US railways. Work in the grocery sector eventually resulted in the UPC code which was first used in 1974. (A packet of Wrigleys chewing gum was the very first item to be read ).Since the first use in 1974, the UPC code became extended to include 2 extra digits to become EAN, which is now probably the most widely used code in the world. Barcode really started to be taken up by industry in 1981 when the US Department of Defence adopted Code 39 for the coding of military equipment.

As time went on, further coding systems were developed and today there are a wide range of different symbologies, available to users.

Barcode is the most widely used identification technology in the world and nowadays there can't be many people on the planet who don't know what a barcode is. It is a very powerful technology, very cheap to produce with a wide range of scanning and printing equipment available in the market at competitive prices. BARCODE TECHNIOLOGIES LTD provides a wide range of barcode scanning equipment which you can find in the products section of this website.

There are those who consider that barcode has had it's day and that RFID tags will soon replace it. This is a very limited view. It is unlikely that barcode will be replaced by RFID certainly for identification at item level, and in the future it is likely that the two technologies will be used side by side, utilising the different strengths of each to suit particular requirements within the same application.

How does it work?

A traditional (linear) barcode label consists of a series of black and white bars of different widths arranged according to a specific set of rules for that particular barcode type or "symbology". A light source from a barcode reader or "scanner" (CCD or laser), illuminates the label, and receiving optics in the scanner head record the returned light signal from the white spaces which reflect the light and the black bars which absorb the light. These reflected peaks and troughs are converted into electronic signals which are then decoded according to the rules for that particular symbology, into ASCII characters.

Many different linear symbologies are available nowadays, including the following:

UPC-Based Symbologies:
UPC-A: Used with consumer products in U.S., 12 characters
UPC-E: Short version of UPC symbol, 6 characters
EAN-13: Used with consumer products internationally, 13 characters
EAN-8: Short version of EAN-13, 8 characters
JAN Codes: Same as EAN-13, used in Japan
Bookland: Used to mark books with ISBN number
UPC-Based Extensions
2-Digit Ext.: Used to indicate magazines and newspaper issue numbers
5-Digit Ext.: Used to mark suggested retail price of books
2 of 5 Symbologies:
Standard 2 of 5: Used in airline ticket marking, photofinishing
Industrial 2 of 5: Same as Standard 2 of 5
Interleaved 2 of 5: Used in warehouse, industrial applications
Pulse Width Modulated Symbologies:
Plessey Code: Old symbology, used for shelf marking in retail enviornments
MSI: Variation of Plessey code, with similar applications
Modified Plessey Code: Same as MSI
Anker Code: Used in European POS systems before EAN was implementated
Code 11 (USD-8): Used to identify telecommunications equipment
Postnet: Printed by U.S. Post Office on envelopes
Codabar (aka Ames Code/USD-4/NW-7/2 of 7 Code): Used in libraries and blood banks

Alphanumeric Symbologies

Code 128 Based Symbologies:
Code 128: Very dense code, used extensively worldwide
UCC/EAN-128: Used to encode shipping/product information
SISAC: Used to encode serial items/periodic magazines
Code 39 (aka USD-3, 3 of 9): U.S. Government and military use, required for DoD applications
Code 93 (aka USS-93): Compressed form of Code 39

Since the late 1980s, the drive to encode ever more information in combination with the space requirements of simple barcodes has led to the development of another form of barcode which has been gaining greater popularity, that is the 2D barcode. Linear barcodes can only ever contain a single string of data which acts as a licence plate ID, i.e. the information about the item to which the barcode label is attached has to be stored in a separate database to which the barcode number acts as a pointer. In order to store more information on the label itself, (item attendant data), the 2D barcode was developed. These barcode labels store data in both the x and y direction, to give the possibility of storing up to 2Mb of data on the label itself. Several different formats of 2D code have been developed.

2-Dimensional (2D) Symbologies

Matrix Codes are a type of true 2D barcode, which do not consist of bars but rather a grid of square cells.

Symbology Notes
3-DI Developed by Lynn Ltd.
ArrayTag From ArrayTech Systems.
Aztec Code Public domain.
Small Aztec Code  
Bullseye Tested in a Kroger store in Cincinnati. Uses concentric bars.
Code 1 Public domain.
CP Code From CP Tron, Inc.
DataGlyphs From Xerox PARC.
Data Matrix From RVSI Acuity CiMatrix. Now Public Domain
Datastrip Code From Datastrip, Inc.
Dot Code A  
HueCode From Robot Design Associates. Uses greyscale or colour.
INTACTA.CODE From INTACTA Technologies, Inc.
MaxiCode Used by United Parcel Service.
MiniCode From Omniplanar, Inc.
QR Code From Nippondenso ID Systems. Public domain.
SmartCode From InfoImaging Technologies.
Snowflake Code From Marconi Data Systems, Inc.
SpotCode Circular code from High Energy Magic Ltd.
SuperCode Public domain.
UltraCode Black-and-white & colour versions. Public domain.

Stacked Barcodes are a compromise between true 2D barcodes and linear codes, and are formed by taking a traditional linear symbology and placing it in an envelope that allows multiple rows, one above the other.

Symbology Notes
Codablock Stacked 1D barcodes.
Code 16K Based on 1D Code 128.
Code 49 Stacked 1D barcodes from Intermec Corp.
PDF417 The most common 2D barcode. Public domain.
Micro PDF417  

What do I need to read a barcode label?

There are a wide variety of bar code reading devices available including the following:

Barcode Wand

For many years this used to be the most popular device for reading barcodes mainly because of cost. Wands or light-pens work by moving the wand's illuminated head across the barcode. As the wand passes across the label, it records the peaks and troughs of reflected light and the time duration of each from which it calculates the width of the bars. However some skill is needed to use one, since it is important that the wand moves at a uniform speed, so not everyone is good at it, and also the lens of the reader tends to wear as a result of constant wiping across barcode labels. As the price of better scanning technology has dropped, wands have lost ground to handheld scanners.

Handheld Scanners

These devices are available in two principal technology formats, laser scanners and CCD scanners.

Laser scanners work by moving a tiny beam of laser light (using an oscillating mirror) in a straight line across a barcode and reading the returned light signals. Considered generally as the premier scanning technology, laser light can be emitted to a considerable distance, and so it is the technology of choice for long range applications, and scanners are available which can read up to 10 metres or so. Because the beam of laser light is linear, for use with 2D barcodes a laser scanning beam has to be "rastered", that is, moved up and down the label in order to get 2D coverage.

CCD scanners work by illuminating the barcode label with a thin line of light usually from an array of LEDs in the head of the scanner, and then taking an image of the illuminated line, on a pixel by pixel basis and then decoding the light and dark spaces. CCDs are either linear, that is they read a thin line of light, for use with linear barcodes, or area, that is they can take an image of the whole area ( e.g. for 2D barcodes), a bit like using a CCD camera. Because the latter works like a CCD camera it can also be used for capturing non-barcode images such as signatures and peoples faces for example, (often also referred to as imagers). In general terms CCD scanners tend to be cheaper than laser scanners.

What do I need to print barcodes?

Dot matrix, laser, and ink jet printers can be used to print barcode labels, but they all have their drawbacks. Thermal label printers are specifically designed for the task and so give the best results. They can print at high speeds and can be used to print single labels at a time, or whole rolls at once.

Thermal Printing Explained.

Thermal printing involves heat transfer from a thermal printhead to a heat sensitive paper or ribbon. The printhead consists of a long, linear array of tiny resistive heating elements that are arranged perpendicular to the flow of the paper. Each element heats the area directly below it on the paper and the image is produced by the rows of dots that are printed onto the paper as it passes beneath the printhead.

There are two basic thermal printing methods:

Direct Thermal Printing (DT)

With this method, the printhead is in direct contact with the chemically treated paper and no ribbon is used. As a result, the running costs are lower, however, this method will also wear down the printhead faster than with thermal transfer as paper is coarse and will wear the printhead down over time. In addition to this the edge of each label strikes the printhead as it passes causing further wear. So although no ribbon is needed, the printhead will wear out faster. Printheads are considered to be consumables and must be included in the overall cost of operation.

This method should be used where the lifecycle of the label is very short, and cannot come into contact with heat or ultra violet light. Thermal paper will mark if scratched and will eventually turn black if left for long periods of time.

Thermal Transfer Printing (TT)

Thermal Transfer printer use the same technology as direct thermal printer. Heat from the printhead is applied to the ribbon, the material on the ribbon is then transferred to the label media. The thermal transfer method will cost more due to the need for a ribbon, but there will also be less wear on the printhead, prolonging its life.

This method should be used where there is a greater label lifecycle required. There is a much higher variety of media stock, which is higher in durability. Also the quality of print is generally higher.