BARCODE KNOWLEDGE
Bar Coding
How does a bar code work?
How do you read a bar code?
How do you print Bar Code Label?
What's a Portable Data Terminal?
POS
What is a PC cash drawer?
Wireless
Glossary
Basic Principles
Host System and Software
Wireless Site Surveys and Installation
Wireless Vertical Markets
Bar Coding
How does a bar code work?
Actually, a bar code works in much the same way as an ordinary flashlight - by reflecting light
upon a surface. The process begins when a light beam is scanned through a bar code, which contains
a small, sensory reading device. This sensor detects the light being reflected back from the bar
code, and converts light energy into electrical energy. The result is an electrical signal that
can be converted into data.
Bar codes are measured by the width of the narrow bar and are recorded in mils, or 1/1000 inch.
A 15 Mill bar code, for instance, has narrow bar that is 15/1000 inches wide.
Further, "quiet zones," or blank spaces to the left and right of bar code symbols, are included
to insure the bar code can be read.
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How do you read a bar code?
First, an input device must convert light energy into electrical energy. There are a variety of
input devices, each with its own unique characteristics. (wand, CCD and laser gun)
CCD Scan: The CCD scanner will bathe the barcode
image in red light and then capture the image on a photosensitive microchip
inside the scanner. The appearance of the pattern will be fuzzy rectangle
of red light. Early and inexpensive CCD scanners required a "close to contact"
distance with the barcode to read. Advances in optics and technology have
extended the distance from the code.
Single-line: Most commonly found with hand held
scanners, the single line pattern must cross the barcode in its length to
read the image. The beam usually appears as a single line, but in reality
is made up of many sweeps of the laser beam over the same path. The single
scan line works very well for "point and shoot" scanning and being able
to pick out a single barcode from a menu. Examples of this would be for
Garden Department items, buld foods or pets where using a barcode on the
item would not be practical.
Multi-line/Raster: In applications where
all of the labels are facing in the same direction and moving, the raster
scan pattern is best. As the barcode moves through the field, there will
be many opportunities to decode the label. A small number of scanners use
this pattern for PDF417 scanning. Example applications would be in industrial
"Can and Bottle machines" and automated production lines.
Omni-Directional/Web: When the scanner is in a
fixed position, mounted in the counter or setting in s stand, the Omni-Direction
pattern will allow barcodes to be scanned with minimal movement by the operator
to position the barcode label. Less operator fatigue and greater thru-put
at the check stand are some of the main advantages. As in the raster pattern
the scanner must have optics to create the pattern. This usually requires
some sort of motor and turning mirror assembly. Generally this will increase
the overall cost of the scanner. Example applications would by grocery,
general retail, and industrial parcel shipping.
Photo Image: Similar to the CCD field, but with
much great resolution, the photo image scan pattern captures the whole barcode
image. The image is then analyzed by the software in the scanner and decoded.
Because the entire image is captured, the scanner can read complex barcodes
such as PDF417 quickly. Another new and emerging application for this type
of scanning is capturing a digitized image of the customers face for future
ID recognition.
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How do you print Bar Code Labels?
Bar codes can be printed with existing dot matrix or laser printers, but with varying results.
Thermal label printers, on the other hand, were designed specifically for the job and are
built to produce high-quality text and graphics. They print at fast speeds and can be used
to print on label at a time or an entire roll.
There are two basic thermal printing methods.
1. Thermal transfer printing In this method, the
print head transfers ink from a ribbon onto standard paper. The thermal
transfer printer brings greater consumable costs because it utilizes a ribbon,
but there is a less wear and tear on the print head.
2. Thermal direct printing In this method, the
print head is in direct contact with treated paper, and no ribbon is used.
As a result, consumable costs are smaller, but the print head undergoes
substantially more wear and tear. A ribbon produces less friction than paper,
so a print head lasts approximately four times longer when printing in thermal
transfer mode than in thermal direct mode.
Every thermal label printer is driven by a proprietary programming language, which can make the
bar code printing process cahllenging. However, bar code label software can make it easier by
allowing you to create labels on the screen and print labels with data from various sources.
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What's a Portable Data Terminal?
Sometimes you must bring the computer to the bar code, particularly to handle jobs such as warehouse
inventory control or freezer applications. A portable data terminal (PDT) - a fully programmable
hand-held computer designed specifically for data collection - is necessary in such instances.
Collected data must be transfered back to the host computer from the PDT, which can be accomplished
in one of two ways. A radio frequency communincations link provides online real-time data communications,
immediate updates to databases and feedback to the operator. However, this solution could require a complex
connection to the host. You application may require a less difficult or expensive method. Batch data
collection is a simpler and easier process.
The operating system of the portable data computer determines the method of programming. Propritary
operating systems usually require knowledge of a proprietaty programming language. Other units may
use a common operating system such as DOS or Microsoft Windows, allowing for programming with a more
common language such as BASIC or "C". Most applications will be unique to the user and are likely to
require custom programming. Programs may be written in a common language, or a program operator may
be used to cut development time.
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POS
What is a PC cash drawer?
A PC cash drawer is a point-of-sale system designed around a standard personal computer. Customers
can add various peripherals to the system to meet their own paticular needs. (receipt printer, cash
drawer, check reader. magnetic card reader, keyboard, scale, display, scanner and software)
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