Barcode Basics

How does a barcode work?

Each character is represented by a pattern of wide and narrow bars. A barcode reader uses a photosensor to convert the barcode into an electrical signal as it moves across a barcode. The scanner then measures the relative widths of the bars and spaces, translates the different patterns back into regular characters, and sends them on to a computer or portable terminal.

There are different barcode symbologies, each with its own particular pattern of bars. The UPC code used on retail products is an all-numeric code; so is the Interleaved 2 of 5 Code. Code 39 includes upper case letters, digits, and a few symbols. Code 128 includes every printable and unprintable ASCII character code.

What's a 2-D code?

2-Dimensional symbols are generally square or rectangular patterns that encode data in two dimensions. They fall into two general categories: 'Stacked barcodes' are constructed like a layer cake of barcodes stacked on on top of the other; they can be read by special 2-D scanners or by many CCD and laser scanners with the aid of special decoding software. 'Matrix Codes' are built on a true 2-D matrix; they are usually more compact than a stacked barcode, and they can be read only by a true 2-D scanner. The primary advantage of 2-D codes is the ability to encode a lot of information in a small space. The practical limit for a standard barcode depends on a number of factors, but 20 to 25 characters is an approximate maximum; 2-D symbols can encode from 100 to about 2,000 characters. The next time you receive a package from UPS look for a 1-inch square label with a pattern of dots and a small bullseye in the center. This is a MaxiCode label, and it is used by UPS for automatic destination sortation. Two other popular 2-D codes are PDF-417 and DataMatrix.

How do I read these codes?

First you will need an input device (barcode reader) to read the barcode. Pen Mobile Solutions stocks a vast range of devices to suit various applications and budgets.

A barcode reader, also called a till scanner, barcode scanner or point-of-sale (POS) scanner, is a hand-held or stationary input device used to capture and read information contained in a bar code. A barcode reader consists of a scanner, and a cable used to connect the reader with a computer. Types include:

CCD Barcode Readers
A CCD scanner has a better read-range than the pen wand and is often used in retail sales. Typically, a CCD scanner has a "gun" type interface and has to be held no more than one inch from the bar code. Each time the bar code is scanned, several readings are taken to reduce the possibility of errors. A disadvantage of the CCD scanner is that it cannot read a bar code that is wider than its input face.

Laser Barcode Readers
A laser scanner, either hand-held or stationary, does not have to be close to the bar code in order to do its job. It uses a system of mirrors and lenses to allow the scanner to read the bar code regardless of orientation, and can easily read a bar code up to 24 inches away. To reduce the possibility of errors, a laser scanning may perform up to 500 scans per second. Specialised long-range laser scanners are capable of reading a bar code up to 30 feet away. Suitable for both retail and industrial applications, progressing technology has also led to laser scanners being available as either tethered devices or cordless.

Digital or Imager Barcode Readers
An image scanner, also called a camera reader, uses a small video camera to capture an image of the bar code and then uses sophisticated digital image processing techniques to decode the bar code. It can read a bar code from about 3 to 9 inches away and generally costs less than a laser scanner. Reliability is equal to if not surpassed by laser scanners as the scan engine within these devices consists of no moving parts, cutting down on the possibility of components becoming loose or breaking if dropped. Suitable for reading 2-D and PDF-417 barcodes.

What interface options are there?
All tethered readers need to be used with a cable, which is used to connect a barcode reader to another device (host), usually a PC, till, portable terminal or laptop. Cables come in a variety of interfaces.

RS232
Enables the user to plug the device into a PC or suitable EPOS till system. Two types are generally available including a 9 pin and 25 pin female D type connector, details of connectors are listed under the product descriptions.

Keyboard Wedge (KBW)
Type of connector on a cable, enables the user to plug the device into a PC and keyboard. The cable plugs into the scanner at one end, usually an RJ45 type plug, from the scanner the cable then splits into two barrel type connectors. In this configuration, the scanner is ‘wedged’ between the PS/2 port on the PC and the keyboard, allowing users to input data without worrying about changing the existing setup.

USB
Connector that allows the user to plug a device straight into the USB port on a PC or till.

How can I print barcode labels?
Barcode labels can be printed from any standard dot-matrix or laser printer, however it is recommended that a thermal printer be used. Thermal printers have been designed specifically for printing barcode labels and are therefore better suited to the task. They can print one label at a time or whole rolls at a time, with various print speeds available to suit your application.

There are two basic thermal printing types:

Direct Thermal Transfer
Direct Thermal labels are made from chemically sensitized paper or synthetics that turn black when heated. A roller advances the labels and squeezes them against the printhead, which contains a row of miniature solid-state heating elements. The printer's internal microprocessor turns the elements on and off to form the image. Using this type of transfer cuts out the need for ribbons therefore reducing consumable costs. However using this form of transfer does cause more wear on the printhead and should be taken into account when considering this option.

A disadvantage is that direct thermal labels tend to fade over time (6 months to a year), and this process can be accelerated by heat, humidity, and exposure to sunlight. So Direct Thermal is suitable for applications where the lifecycle of the label is very short, such as courier labels.

Thermal Transfer
A Thermal Transfer printer uses a thin plastic ribbon with a thin coating of wax or resin based pigment. The ribbon and labels feed from separate rolls and are squeezed together by a roller as they pass under the thermal printhead . The heating elements in the printhead melt the coating which transfers to the label to form the image.

Produces a durable, high-quality image, and can be used with many types of label stocks (paper and synthetics). Printers are durable and offer relatively fast printing speeds; some models approach 12 inches per second. Cost of printing a single color (usually black) is reasonable, but multi-color printing can be expensive in terms of printer cost and consumption of ribbons.

Excellent for producing product and packaging labels either on demand or in batches.

What is DPI?
Dots per inch (DPI) is a measure of printing resolution, in particular the number of individual dots of ink a printer or toner can produce within a linear one-inch (2.54 cm) space. Up to a point, printers with higher DPI produce clearer and more detailed output, therefore applications where smaller, denser codes are needed the higher the DPI.

Will I need software to run the printer?
Most printers come packaged with the necessary printer drivers, which will allow you to print from basic packages such as word. For the best results we suggest using Barcode Label Design Software which is flexible, easy to use and compliments your application more effectively.