Barcode Technology - Code 39Ext Barcode               Hide the description

Code 39 Ext (Code 39 Extended) supports all ASCII 128 characters by using double character encoding.

For example, the lower-case letter "a" is represented by "+A". Because of the possibility of misrepresentation of a symbol, most bar code scanners must be switched to extended mode in order to recognize Code 39 Extended.

Code 39 (also known as Alpha39, Code 3 of 9, Code 3/9, Type 39, USS Code 39, or USD-3) is a variable length,

discrete barcode symbology.

Valid characters:  0123456789[Space]ABCDEFGHIJKLMNOPQRSTUVWXYZ-.$/+%

Code 39Ext is one of the many barcode formats currently in use.

A Barcode is a method of representing data in a visual, machine-readable form.

The barcode formats has two categories:

One-dimensional (1D) --- Barcodes represented data by varying the widths and spacings of parallel lines.

Two-dimensional (2D) --- Using rectangles, dots, hexagons and other geometric patterns to represented data.

Code 39 can be to produced in different proportions: 2,0:1 and 3,0:1. This is the proportion between the thin and the

thick lines of the code. As higher the proportion, the wider is the printed barcode with same contents, but even better is readability.

The * character of Code 39:

The * character presented below is not a true encodable character, but is the start and stop symbol for Code 39. The asymmetry of the symbol allows the reader to determine the direction of the barcode being scanned. This code is traditionally mapped to the * character in barcode fonts and will often appear with the human-readable representation alongside the barcode.

In order to create this code do not have to enter the stars: If the text line shows *1234* you just have to enter 1234 because the stars are a fixed part of Code 39.

Check digit:

Since Code 39 is self-checking, a check digit normally isn't necessary. However, in applications that require an extremely high level of accuracy a modulo 43 checksum digit may be added.
To calculate the optional checksum digit, follow the following steps.
Take the value (0 through 42) of each character in the bar code. The start and stop characters are not included in the checksum calculation.
Sum the value of each of the values of each of the characters described in step 1.
Divide the result from step 2 by 43.
The remainder from the division in step 3 is the checksum character that will be appended to the data message before the stop character.

Drawback:

Possibly the most serious drawback of Code 39 is its low data density: It requires more space to encode data in Code 39 than, for example, in Code 128. This means that very small goods cannot be labeled with a Code 39 based barcode. However, Code 39 is still used by some postal services (although the Universal Postal Union recommends using Code 128 in all cases), and can be decoded with virtually any barcode reader. One advantage of Code 39 is that since there is no need to generate a check digit, it can easily be integrated into an existing printing system by adding a barcode font to the system or printer and then printing the raw data in that font.

Human Readable:

Most barcodes display their corresponding values below them, which makes it possible to human read and manually  enter the barcode values into the equivalent system when the barcode label is worn out and cannot be read by the barcode scanner.

Advantages:

Using Barcode system eliminates the possibility of human error. The error rate of manually entering data is
significantly higher than that of scan barcodes. Barcode scanning is fast and reliable, and it takes much less time than manual data entry. Especially when using a QR code, hundreds of characters can be read and entered into your system instantly.

Using a barcode system can make the working process simple and easy, so it can reduces the employee training time. It only takes a few minutes to master the barcode scanner to collecting data, employees no need to familiar with the entire inventory or pricing process. This also reduces the cost of employee training.

History:

Code 39 was developed by Dr. David Allais and Ray Stevens of Intermec in 1974. Their original design included two wide bars and one wide space in each character, resulting in 40 possible characters. Setting aside one of these characters as a start and stop pattern left 39 characters, which was the origin of the name Code 39. Four punctuation characters were later added, using no wide bars and three wide spaces, expanding the character set to 43 characters.

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