What is a Plessey Code?

what are plessey barcodes

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Have you ever heard of the term “Plessey Code”? It’s probably a foreign concept to many people. But if you’re in the retail, logistics, or manufacturing industries, chances are you’ve come across this technology before. 

Plessey code is a continuous, variable-length linear barcode symbology that was developed by a British-based electronics, defence and telecommunications company, The Plessey Company plc, in 1971. Plessey was based on pulse-width modulation and is used to encode hexadecimal data.

Plessey code has a higher density than other popular symbologies, such as Code 39, making it more suitable for use with dot matrix printers. Originally, Plessey code was designed for use in libraries, but its use in this context has become rare.

In this article, we will examine the Plessey code and everything you need to know about it.

What is a Plessey Code? - A Deep Explanation

Plessey Barcode

Plessey code is a 1D barcode symbology developed in 1971. This barcode comprises alternating bars and spaces of varying widths, which can be machine-read via optical scanners. The Plessey barcode was the first of its kind and was used mainly in supermarkets for their product restocking systems.

The chief advantages of the Plessey code are its simplicity and relative ease of printing using dot-matrix printers, both popular technologies at the time of the barcode’s introduction. The barcode also has a slightly higher density than the more common barcode, Code 39.

Plessey code supports hexadecimal characters, meaning that the barcode encodes digits from 0 to 9 and uppercase letters from A to F. It uses a cyclic redundancy check (CRC) for error correction.

Despite being an early pioneer in barcode technology, it is not widely used today, mainly due to a lack of technical specifications. Plessey codes were mainly available on paper documents which have now been discontinued.

How to Recognize a Plessey Barcode?

How to identify a Plessey barcode

The easiest way to recognize a Plessey code is to look for its distinct pattern.

A Plesssey barcode should start with the forward start code – 1101 followed by encoded data, checksum code, terminating bar and reverse start code – 0011, ending with trailing quiet zone.

Unlike other barcodes, Plessey codes do not have a limited number of digits or letters and can be both short and long in length. They are capable of encoding numeric characters as well as uppercase letters A through F.

However, Plessey codes have become less common over time due to the development of more modern barcode technologies.

How Does a Plessey Code Work?

Plessey barcodes are composed of a series of vertical bars and spaces of varying widths. The bars are formed from black and white lines, which can be read by a barcode scanner. These scanners detect light and dark lines on the barcode as it passes over them to decode the hexadecimal values encoded in it.

MSI Plessey - The Variations of Plessey Code

The MSI Plessey barcode is a 1D barcode symbology used in warehouses and other storage facilities for inventory control. It was developed by the MSI Data Corporation based on the Plessey code symbology.

The MSI Plessey barcode encodes only digits 0–9 and does not support letters or symbols. MSI Plessey codes have no restriction on the amount of data that can be encoded, allowing them to store more information than other barcode formats.

Today, MSI Plessey barcodes are primarily used as shelf tags in supermarket and retail stores, warehouses, and other storage facilities to maintain accurate records of items and keep better track of stock levels. 

Variation of MSI Plessey Barcode

How to Get a Plessey Code?

Generating Plessey barcodes is an easy and cost-effective way for businesses to identify and track their products. With the help of online tools and free barcode generators, you can create your own codes in just a few simple steps.

By simply entering the numerical digits associated with the product into the barcode generator, the user can get a customized Plessey code that is ready for printing and implementation. This convenient process offers accessibility to anyone who wants to take advantage of the benefits of having a Plessey code.

Additionally, there’s no need to pay a fee to get a Plessey code; they are old and discontinued barcode symbology. Even though GS1, an organization dedicated to supporting global barcoding standards, doesn’t provide this type of barcode, it’s still used by various businesses for internal communications.

Plessey Code Barcode Anatomy

Anatomy of Plessey code barcode

The Plessey code has a distinctive structure consisting of.

  • Leading Quiet Zone
  • Forward Start code
  • Encoded Data
  • Checksum Code
  • Terminating Bar
  • Reverse start Code
  • Trailing Quiet Zone

Leading Quiet Zone

The leading Quiet Zone is necessary for efficient scanning and must be at least 0.125 inches wide on either side of the barcode.

Forward Start Code

The leading Quiet Zone is followed by the forward start code of 1101, which indicates the beginning of the barcode.

Encoded data

Encoded data follows the forward start code, representing each digit by four bars or bits. A wide bar followed by a narrow space signifies a 1 bit, while a narrow bar followed by a wide space represents a 0 bit.

Checksum Code

To ensure the accuracy of the barcode, a two-digit checksum code is appended to the data and calculated using a formula known as a Cyclic Redundancy Check (CRC). 

Cyclic Redundancy Check a full pitch bar that uses a polynomial to compute the check digit. The polynomial used to generate the checksum is –  g(x) = x8 + x7 + x6 + x5 + x3 + 1. 

Termination Bar & Reverse Start Code

Finally, there is a terminating bar followed by the reverse start code of 0011, which helps detect the scan direction to read and decode the symbol correctly from left to right or right to left. 

Trailing Quiet Zone

To end off, there’s another trailing Quiet Zone that must be at least 0.125 inches wide on either side for efficient scanning purposes.

Designing and Printing Rules of Plessey Codes

List of four designing rules of plessey code

Dimensions of Plessey Codes

The dimension of the bars and spaces of Plessey barcodes are precisely defined, as stated by the regulations. The bars and spaces must have a ratio lower than 1. The space width must be less than 0.229 mm, while the bar width must be higher than 0.127 mm.

Additionally, both before and after each Plessey code, there must be a margin of 4 bits. This ensures that scanners or other barcode readers can correctly decode the barcode.

Printing of Plessey Codes

List of three printing rules of Plessey code

Plessey codes were traditionally printed with dot matrix printers. However, today’s technology allows for more efficient and cost-effective ways to print barcodes. The most popular and reliable method is thermal printing, which uses heat to create the desired barcode image.

Plessey codes do not have a strict printing requirement, although certain guidelines must be followed to ensure accuracy.

A Plessey barcode must feature a contrast ratio of at least 45 (absolute white and absolute black), and the intensity must be higher than 50% for it to be successfully scanned. Furthermore, any bends or deformations in the symbol should be avoided.

Plessey barcodes should be printed on non-glossy paper with a printing resolution of at least 203 dpi for best results.

Thermal printers are a great choice for businesses as they print at high speed, have low maintenance costs and deliver high-quality results. The setup cost of thermal printers is higher than traditional dot matrix printers, but in the long run, it’s much more economical.

Triton Store is your one-stop shop for all thermal barcode printing needs. We offer a range of thermal printers to suit your business requirements and budget. We provide a broad selection of thermal printers from reputable manufacturers like Honeywell, Zebra and TSC. Our extensive inventory offers a variety of printer models, including direct thermal printers, thermal transfer printers, barcode label printers, desktop printers and industrial printers.

We also offer a variety of print consumables, such as thermal labels and ribbons. Our print consumables are manufactured to the highest standards with superior adhesion and long-lasting print quality. Our range of thermal printer consumables includes thermal transfer ribbons, thermal labels, thermal carton labels, thermal carcase tags, and food-compliant thermal inserts.

Triton also offers the world leading barcode label design software BarTender in four different editions, Starter, Professional, Automation and Enterprise.  Our solution experts can quickly help you establish the right version for your needs so feel free to get in touch with us and we can book in a session.

Wrapping Up

There’s no denying that Plessey codes offer businesses an efficient way to keep track of their products without being overly complicated or expensive. While they may not be as popular as they once were, thanks to newer barcode technologies, they remain an invaluable tool for anyone who needs reliable data tracking in their business operations.

With the knowledge provided in the article, you’ll now be able to take full advantage of all the benefits of using a Plessey code for your business.

We hope this article has given you a better understanding of Plessey codes and how to implement them in your business operations.

Thanks for reading!

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