Bar Coding

Reading Between the lines

Bar Codes have infiltrated every facet of our lives; you'll find them in grocery stores, hospitals,department stores, on farms, even in your own home. Bar coding is a proven technology in use for more than last 30 years and finds large scale acceptance as the best possible method of accurate and faster data entry into the user's system. Bar codes are just a different way of encoding numbers and letters by using a combination of bars and spaces of varying widths. Think of them as another way of writing since they replace key data entry as a method of gathering data. In business, the correct use of bar codes can reduce inefficiencies and improve a company's productivity thereby growing their bottom line.

Simply put, bar codes are a fast, easy, and accurate way of entering data. This may come as a surprise to you! A bar code doesn't contain descriptive data. Just as your social security number doesn't contain your name or address, a bar code is just a reference number that a computer uses to look up an associated record that contains descriptive data and other important information.

How Bar Codes are Read

Bar codes are read by sweeping a small spot of light across the printed bar code symbol. Your eyes only see a thin red line emitted from the laser scanner. But what's happening is that the scanner's light source is being absorbed by the dark bars and reflected by the light spaces. A device in the scanner takes the reflected light and converts it into an electrical signal. The scanner's laser (light source) starts to read the bar code at a white space (the quiet zone) before the first bar and continues passing by the last bar, ending in the white space which follows it. Because a bar code cannot be read if the sweep wanders outside the symbol area, bar heights are chosen to make it easy to keep the sweep within the bar code area. The longer the information to be coded, the longer the bar code needed. And as the length increases, so does the height of the bars and spaces to be read .

The barcode scanners come in various varieties depending upon application requirements. From technology point of view, the scanners are mainly of three types: CCD, Laser and Digital Imagers. From application point of view scanners are mainly of 4 types: Fixed scanners, Key board wedge readers, Serial bar code Scanners, USB scanners.


Symbology is considered a language in bar code technology. Just as you might speak French while traveling in France, a symbology allows a scanner and a bar code to "speak" to each other. When a bar code is scanned, it's the symbology that enables the information to be read accurately. And then when a bar code is printed, it's the symbology that allows the printer to understand the information that needs to be turned into a label.

Bar Code Scanners

Barcode scanner is a device, which is used to read the barcode and decode the bar coded data to a PC or Host system. One of the most common methods of reading barcodes is by use of the hand held barcode scanner. The barcode scanners have built-in decoders and can read several different barcode types. Most of the scanners receive their power from the PC keyboard or USB port so no external power supply is required. In case of serial connectivity (RS232), the external power supply is required since no power is available through RS232 port.

When a barcode is scanned in, the data is sent to your PC as if it had been typed by the keyboard (in case of Keyboard & USB). Most barcode scanners can read common linear symbologies such as Code 39, UPC, EAN, Code 128 and Codabar. Based upon scanning technology the scanners can be classified as CCD (Charged Couple Device) and Laser scanners. From application point of view, the scanners can be classified as Hand Held Scanners, Fixed Mount, Flatbed and Cordless scanners.

Bar Code Printing

The variety of technologies available for bar code printing can be overwhelming. The barcodes can be printed on existing Laser/Inkjet or Dot Matrix Printers and can be purchased in the pre-printed format.

Dot Matrix technology uses a hammer or pin to transfer pigment from a ribbon onto the substrate. Due to the inaccuracy of dot placement and low resolution of the printing technology, these printers are nearly unusable for bar coding.

Ink jet printing is used primarily for printing cartons or product packages with barcodes and human-readable data at very high speed. Ink jet printers spray ink onto the label surface in either a continuous stream, covering the entire print width with one spray, or one drop at a time. However, ink jet printing is not acceptable for most bar coding applications.

Laser printer works much like a photocopier; it projects controlled streams of ions onto the surface of a print drum, resulting in a charged image. The charged image then selectively attracts toner particles, transferring the image onto the paper substrate. After the image is transferred to the media, the heat and pressure of the fuser cause the image to adhere to the media.

The most widely used technologies for dedicated bar coding systems are Direct Thermal and Thermal Transfer printing. Both technologies use a heated print head to create the image on the label; however, they are suited to different applications.

Direct Thermal printing utilizes heat-sensitive media that blackens as it passes under the print-head. Because they print without a ribbon, direct thermal printers are noted for their simplicity. Direct thermal printed labels typically have a considerable shelf life but are not well suited for environments that expose them to heat, long periods of direct sunlight, or abrasion.

Thermal Transfer printed labels are easily identified by the crisp, often glossy, printed surface. The clarity is achieved by using a thin ribbon roll that when heated by the print-head melts onto the label to form the image. When matched with suitable media, thermal transfer technology is not only impervious to heat and moisture, but the image cannot be rubbed off, making the printed labels the most durable available. An additional benefit of this technology is the continuity of the printed image. Because the color and density of the printed image is determined by the ribbon and the resolution of the printer, thermal transfer printing produces consistent, reliable printing on every label.

Typical Applications for Bar Coding

  • Retail, POS
  • Receiving and Put away
  • Warehouse and Inventory Management
  • Work - In - Process tracking
  • Transportation and Logistics
  • Shipping and Distribution