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Working of a Keyboard Wedge Barcode Scanner

Omkar Phatak Jan 22, 2019
A keyboard wedge barcode scanner is widely used nowadays, as its relevant labeling system is used to code the prices and information of all consumer products. To know more about the working and operating principle of these devices, keep reading ahead.
The keyboard wedge barcode scanner is almost an indispensable device now, in all shops and superstores. The reason for this indispensability, is the popularity of the barcode system.
Every product in the market is now branded with one, which has the price information, as well as the product information, encoded into it. The working and the installation of the scanner is a simple process, which is explained further.

Barcode System

Barcodes are a series of black lines with white spacing in between. They form a symbolic, encrypted language, that represents alphanumeric characters. There are different codes used to encode data, which vary amongst manufacturers.
The software used on a computer, to read the barcode, has to have the specification of the coding standard used, so that it decrypts it correctly.
The inspiration for the invention of the barcode came from the Morse code. They are like graphic Morse codes. The widths of the black lines, white spaces, and their sequences are used to define a language, that has a barcode analog symbol, for every word or number. The code starts and ends with an extended white space, called the 'silence zone'.

How Does it Work?

Any book you buy or almost any other commodity has its own unique barcode. In a supermarket, when you check out, all of your billing is done by using a device which reads the pricing of each commodity, encoded in the barcode. That device is known as a keyboard wedge barcode scanner.
It's named so, as it is 'wedged' or placed between a keyboard and the computer. This scanner is attached to the computer, by replacing the keyboard at its port. That is, the keyboard is unattached from its port and the scanner terminal is connected in its place.
Then, the keyboard is attached to the end of the scanner, which has an extra connection for the purpose. In this arrangement, the keyboard continues its function normally.
The advantage of this arrangement is that the computer identifies the scanner as a keyboard. Therefore, whatever data is sent by the scanner to the computer, is identified as keyboard input. Of course, for this to happen, the scanner has to have a facility to read the data and convert it into ASCII code.
The technology that makes reading of barcode possible with a scanner is the CCD (Charge coupled device) technology. A CCD panel is an array of photosensitive cells, that generate electric currents and have shift registers which constitute its memory element.
When the reader scans a barcode, the ambient light reflected from it, falls on the CCD. This light is of varying intensity and generates a varying current output from the photosensitive cells.
An image of this varying intensity pattern is generated by the charge coupled devices, in the form of a varying voltage pattern. This pattern is then read and decrypted into numbers or alphabets, by the internal mechanism of the scanner.
These numbers and alphabets are then converted into corresponding ASCII codes, just like a keyboard. The data that is read from the barcode, is interpreted as keyboard input by the computer and gets typed in whichever software application is open for billing purpose. Like a keyboard input, it gets entered, wherever the cursor is placed in the application.
The disadvantage of using this device is that it cannot process the read data, from the barcode. It serves the decoded data, without any changes. One cannot parse the data, classify it, or place it in separate boxes. So it is good for general applications. If one wants an advanced pre-processing of decoded data, then some other type of scanner must be used.
The scanner is a simple device, that you can use in your shop or store, to read barcodes and identify prices. With this scanner and the software that reads and processes its output, you have a complete billing solution for your shop.