What are barcodes?

A barcode is simply a graphical representation of a string of characters encoded such that it can be read by a barcode scanner. There are two types of barcode; 1D and 2D. 1D (one dimensional) barcodes are a sequence of vertical lines. They are used to encode a small number of characters (usually numbers). You will see these most commonly on consumer products, used as a unique identifier for a particular product. They are called one dimensional as only the distance between each vertical line is important to the decoding of the barcode.

2D (two dimensional) barcodes are less common. These consist of a sequence of 'blobs' positioned within a box. The vertical and horizontal location of a 'blob' is important to its meaning. 2D barcodes require a special type of barcode scanner; one that can read in both the horizontal and vertical axes. The advantage of 2D barcodes is that they can store larger amounts of information in a small space. Because of this they are often used by couriers and haulage firms to store information on parcels. Details of a package including its weight, content and the delivery name and address can all be encoded within a single 2D barcode (hence their popularity in this field).

What types of barcode scanner are there?

There are two main types of barcode scanner - CCD and laser.

CCD scanners tend to be cheaper than laser scanners. A CCD scanner works by shining small lights (LEDs) onto a barcode and reading the reflection from it. The disadvantage of CCD scanners is that they often find it hard to read poorly printed barcodes or barcodes positioned in an awkward manner (such as over a curve).

Laser scanners work by shining a laser beam across the 'scan field' (the space in front of the barcode scanner) and reading the reflected laser light on return to the scanner.

In addition to this there are two types of laser scanner; linear and omni-directional. Linear scanners emit a horizontal beam. This means that they must be positioned such that the beam reads across the barcode. Omni-directional scanners emit a circular pattern of laser light which can read a barcode presented to it at any angle.

In addition to this barcode scanners can either be desk mounted or hand held. Desk mounted scanners ('presentation' scanners as they are known) sit on a counter or desktop and barcodes are brought to them for scanning (eg. those used in supermarkets). Hand held scanners require the operator to take the scanner to the barcode.

Things to consider when choosing a scanner

You should think carefully about what type of scanner you need before investing - barcode scanners are expensive and choosing the right scanner is important. Sometimes it can also be tempting to 'buy cheap'. Don't. It is far better to spend more money on the right equipment than snap up a cheap scanner that doesn't properly suit your needs.

CCD or laser?

Are the barcodes you will be reading good quality ? Are they clear to read and printed on a flat surface? Is contact with the barcode possible? Is speed of scanning not an issue? If you can answer YES to all these questions then a CCD scanner should be perfectly adequate.

Handheld or deskmount presentation?

Are most of the barcodes being read attached to articles which can be easily lifted/moved? (Usually presentation scanners can be removed from their desk mounting, so it is possible to cope with a small number of large goods). Is it feasible to bring the barcodes to the scanner ? Point-of-sale is an ideal application for a presentation scanner. Warehouse stock-taking is not!

Linear or omni-directional

It's a good idea to go with omni-directional if you're after a presentation scanner. Presenting barcodes to a linear desk mounted scanner can be cumbersome. If you're going for the handheld option then omni-directional is a little overkill; but certainly worth considering if scanning speed is important.

Wireless?

If wandering around with the scanner would be helpful (e.g. if the barcoded goods are located far from the terminal) then it's a good idea to go for a wireless (RF) scanner. These can be expensive so it may be worth considering a simple extension cable if your budget won't stretch. Some wireless scanners are short range only (3m), which may seem pointless BUT you don't have the inconvenience of a cable.

Keyboard or RS232 interface?

You should also consider how the scanner is to connect to your computer. Most scanners provide for RS232 (COM port) or keyboard output. The keyboard interface allows the scanner to share the keyboard port with the keyboard. Barcode data from the scanner is inserted at the caret/cursor position, as if you had typed the characters making up the barcode into the keyboard. No special driver software is required.

If you wish to use the scanner through the RS232 (COM) port then you will need to check that the software you wish to use the scanner with provides support for this method of input. If you are unsure then it's best to go with a keyboard interface.