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Bar Code Basics How does a bar code work? SYMBOLOGY is a term that describes how bar codes work. Bar
codes are made You can also email us your technical support questions Click Here A bar code works like a light when turned on in a dark room. You see the walls and furniture in the room by the reflected light from these items. The scanner device directs a light beam at the bar code. The device contains a small sensory reading element. 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. It's like sonar or radar. 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 a narrow bar that is 15/1000 inches wide. The space between the bars is created using the same mil thickness and is part of the structure. What is used to read bar codes? A bar code scanner is an input device that translates the reflections into electrical energy. There are three types of input devices, all which work different from each other. Because of this some work better than others. Input Devices PEN WANDS-The "wand" is the
original input device. It is durable and contains no moving parts. CCD SCANNERS- The CCD, or
"Charge Couple Device," is another common input device. A CCD is a LASER SCANNERS- The laser
scanner is the most popular bar code input device. IMAGE SCANNERS- The IMAGE
scanner is becomming a more popular bar code input device. DECODERS-Most bar code scanners
decode the signal within the scanning device. These are called "Decoded
scanners". Others depend on a decoder device to interpret the
A decoder that is separate from the scanner costs more because you are buying two devices. The main advantage is that the decoder can provide service to more than one scanner and a credit card reader, thus reducing the cost for hardware. Decoders are usually called "Wedges" because they connect between the keyboard and CPU. (Some connect to the serial RS-232 port). Choosing the right device
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up of bars with confirming spaces between the bars. The
arrangement of bars and spaces is controlled by symbology coding for
different types of bar codes. Popular bar code symbologies are Code39,
UPC-A, EAN, Code128, and the type you see on mail.
It must,
however, come into contact with the bar code, which can present a
challenge. Bar codes can become smeared from repeated scanning. Also, the
wand is controlled by hand movement," meaning it must be held at the
proper angle and moved at the proper speed. For these reasons, a wand is
difficult for some people to use. It is the best choice when cost is the
largest determining factor.
very
"aggressive" instrument, with a high ability to read bar codes quickly and
easily. However, it has two primary limitations. It has a short "read"
range of no more than 1 inch from the bar code. In addition, the CCD has a
limited width, and will not read bar codes that are wider than the face of
the input device, normally 2.75-3.0". It is popular for point of sale
applications. It is not recommended for liquor stores because of moisture
on cans or bottles.
It need not be
close to the bar code to do its job. Laser scanners can read a bar code
from about 6 to 24 inches away, depending on the model. A long range
scanner can read to 30 feet away.
It can read a bar
code from about 3 to 9 inches away. It works and looks like a laser. The
beam covers more area and is easier to target the bar code with it. The
other deciding factor is the price. It sells for less than the laser
scanners.
signal.
These scanners are "Non-decoded scanners". They depend on the decoder to
change the input. The decoder is an electronic device serving three
functions: