Chapter 17: The Defunct 1D - MSI Plessey |
In Brief: |
MSI Plessey is a relic from the dawn of the barcode era. Developed in the early 1970s, it was one of the first symbologies used in retail environments, specifically for labeling supermarket shelves and tracking inventory in warehouses. Its design, based on simple binary encoding, made it easy to print with the technology of the time but also made it highly susceptible to misreads. The lack of robust error correction, combined with the rise of standardized codes like UPC and EAN for point-of-sale, led to its rapid decline. Today, MSI Plessey is virtually extinct in retail and is rarely seen outside of niche, legacy systems. This chapter explores its technical origins, its specific applications, its fatal flaws, and its ultimate replacement by more reliable standards. |
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Introduction: The Ghost in the Retail Aisle |
To the casual observer, a barcode is just a barcode. It is a series of black and white lines that, when scanned, magically brings up a price or product name on a screen. However, the world of automatic identification is a vast ecosystem, a jungle of symbologies each designed for a specific purpose. Some are designed for high density, some for high security, and some---like the subject of this chapter---simply for a specific moment in time. |
MSI Plessey is a fascinating chapter in the history of barcodes because it represents the 'early adopter' phase of the technology. It was a solution developed before the industry had standardized, a tool built for an internal need that was quickly superseded by global systems. It is the ghost of retail aisles past, a code that once guided stock clerks and now serves as a museum piece for technology historians. |
This chapter will dissect the MSI Plessey symbology. We will look at its binary underpinnings, its specific role in the supply chain, the reasons for its spectacular decline, and the lasting lessons it offers about standardization and reliability in data capture. |
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The Genesis of the Code |
The story of MSI Plessey begins in the United Kingdom in 1971 . The Plessey Company, a British electronics, defense, and telecommunications firm, developed the original Plessey Code as a proprietary method for tracking items . This was a time before the Universal Product Code (UPC) had even been formally adopted in the United States, which happened in 1974. The landscape was fragmented, and companies often developed in-house solutions to solve specific logistical headaches. |
The original Plessey Code was quickly adopted by major British retailers. Sainsbury's, a prominent supermarket chain, was among the first to deploy it for product restocking systems . The system was so successful in its limited scope that it began to attract attention. However, the original Plessey Code had drawbacks, primarily related to reading reliability. |
Enter the MSI Data Corporation. They saw the potential of the Plessey Code but recognized its weaknesses. They developed a modified version, which became known as MSI Plessey (sometimes referred to as 'Modified Plessey') . This modification primarily involved the addition of a second check digit to improve accuracy. It was this version, maintained today by Symbol Technologies (now part of Zebra Technologies), that would see the most widespread use . The code is also known by a variety of other names, including Texlon Code and Anker Code, reflecting its fragmented licensing and application history . |
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The Architecture of Obsoletion: Encoding and Structure |
To understand why MSI Plessey failed, we must understand how it worked. It is a numeric-only symbology, capable of encoding digits 0 through 9 . This immediately limited its application to contexts where letters were unnecessary. |
The encoding scheme is based on a simple binary representation. Each character is represented by a pattern of 'zeros' and 'ones' (narrow and wide bars) . In fact, it is so straightforward that, with some practice, one could visually read the code by looking at the width of the bars and spaces . This binary coding made it easy to generate with the dot-matrix printers prevalent in the 1970s, which were not capable of producing the complex variable-width patterns of more sophisticated codes. However, this simplicity is also the source of its fatal flaw. |
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The Structure |
An MSI Plessey barcode is structured as follows : |
1. A Start Character: A distinct pattern (a wide bar followed by a narrow space) to signal the beginning of the barcode to the scanner. |
2. Encoded Data: The sequence of numeric digits that represents the actual data. |
3. Check Digit(s): One or two check digits appended to the data to provide a basic level of error detection. |
4. A Stop Character: A distinct pattern (a narrow bar, a wide space, and another narrow bar) to signal the end of the code. |
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The Problem: No Self-Checking |
The critical technical deficiency of MSI Plessey is that it is not a self-checking symbology . In a self-checking barcode, the encoding of each character includes built-in redundancy. If the scanner misreads a bar as a space, or vice versa, the resulting character is invalid by design, and the scanner can immediately reject it. Code 39, for example, is self-checking because every character contains five bars and four spaces, with two of the bars being wide. |
MSI Plessey does not have this feature. A misread in a single element (a bar read as a space) can easily translate into a different but still valid digit. This made it 'one of the most error-prone of all barcode languages' . To mitigate this, the MSI variant mandated the use of check digits. It supports several check digit algorithms, most commonly Modulo 10, Modulo 11, Modulo 1010, and Modulo 1110 . The check digit provides a mathematical check that the data has been read correctly, but because it is a calculation based on the misread data, it is still theoretically possible to misread a whole sequence and still have the check digit pass. For an industry requiring high throughput, these frequent misreads were a significant operational cost. |
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The Dominant Use Case: Shelf Labels and Internal Inventory |
With these technical characteristics in mind, we can look at its primary application. MSI Plessey was never intended to be a Point-of-Sale (POS) code for consumer checkout. That role was always destined for the likes of UPC and EAN. Instead, MSI Plessey found its niche in the back-end operations of retail: internal inventory control. |
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The Supermarket Shelf Edge |
The most iconic use of MSI Plessey was on the front edge of supermarket shelves, also known as 'shelf talkers' or 'price rails' . If you walked into a supermarket in the 1980s, you would see a small barcode printed on the plastic strip that held the price labels. This was likely an MSI Plessey code. |
This code was not for the customer. It was for the store's internal restocking system. Stock clerks, often using portable data terminals, would scan these shelf labels to verify that a specific product was supposed to be at that location . This system was used to manage inventory levels, confirm delivery accuracy, and maintain shelf planograms. It was a vital tool for warehouse-style grocery stores. |
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Warehouses and Storage Containers |
Beyond the retail floor, MSI Plessey was used in warehouses and distribution centers. It was applied to storage containers and racks to identify locations and track the movement of goods . The fact that it could be printed cheaply and easily was a major advantage. At the time, a warehouse manager could buy a dot-matrix printer and some adhesive labels and create a complete labeling system for a fraction of the cost of more complex proprietary systems. |
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Libraries |
The original Plessey Code saw some use in libraries for tracking books . However, even in this application, it was quickly superseded by more reliable or versatile symbologies like Code 39, which could encode both letters and numbers (allowing for ISBN encoding). |
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The Rise of the Rivals: Why MSI Plessey Became Extinct |
Despite its early adoption and niche usage, MSI Plessey's fate was sealed by the inexorable march of technology and standardization. |
1. The Inefficiency of Numeric-Only Encoding |
The most significant limitation of MSI Plessey was its inability to encode letters. The retail industry quickly recognized the need for more than just numbers. While a shelf label might only need a location code, product serial numbers, batch numbers, and other inventory data often used alphanumeric combinations. The lack of a character set beyond 0-9 made MSI Plessey a dead end for expanding applications . |
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2. The Threat of Misreads |
As scanners became faster and more powerful, the weakness of MSI Plessey's non-self-checking design became a critical liability. In the high-stakes environment of a warehouse or busy store, a misread could lead to inventory discrepancies, ordering errors, and lost sales. While the check digit offered a safety net, it was not a panacea. Furthermore, the code is described as having a low density compared to more modern codes . The binary encoding, while simple, was bulky. It did not pack data as efficiently as other 1D codes, taking up more horizontal space for the same amount of data. |
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3. The Standardization Earthquake: UPC/EAN |
Ultimately, the primary reason MSI Plessey is defunct is the global standardization of retail barcodes. The adoption of the Universal Product Code (UPC) in the US and the European Article Number (EAN) in Europe created a standardized system for identifying products . |
Crucially, these codes were designed for the cash register. The UPC/EAN code on a bag of chips is scanned at the checkout to look up the price. But once the Point-of-Sale system was digitized, the ability to track inventory became automated. |
When a cashier scans the UPC/EAN of a product to sell it, the store's computer system automatically deducts one unit from the inventory. This real-time data is infinitely more valuable than a clerk manually scanning an MSI Plessey shelf label to confirm that a box of cereal is where it should be. |
Why would a store invest in maintaining a separate, internal barcode system (MSI Plessey) for shelf labels when the POS data from the standardized UPC/EAN system could tell them exactly what was being sold and what needed to be reorderedThe economic incentive to maintain the legacy system evaporated. |
UPC/EAN could also be printed on products by manufacturers. This meant retailers no longer had to print labels for stock control; the label was already on the box. The supply chain had been digitized from manufacturer to consumer, making the internal shelf-labeling system redundant. |
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4. Code 128 and the Next Generation |
Even if a retailer wanted to use a separate code for internal use (like warehouse racking), they would not choose MSI Plessey. They would likely choose Code 128, which is widely recognized as superior . Code 128 is high-density, encodes a full ASCII character set, is self-checking, and is highly reliable. For a business, the reduction in scanner errors and the ability to encode more information in a smaller space justified the adoption of newer, superior symbologies . |
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MSI Plessey and Code 39: A Contrast in Applications |
Often, discussions of legacy barcodes lead to Code 39. While they are contemporaries, their applications and survival have been remarkably different. The user request for this chapter emphasizes the technical features of Code 39, so let us examine how Code 39's features affected its application profile compared to MSI Plessey. |
Alphanumeric Capability: Code 39 encodes digits, uppercase letters, and several special characters (space, -, ., $, %, /, and +) . This made it suitable for military logistics (LOGMARS), automotive parts identification, and government applications where item numbers contained letters. MSI Plessey's numeric-only limitation confined it to simple tracking numbers. |
Self-Checking: Code 39 is inherently self-checking. Every character in Code 39 contains exactly five bars and four spaces, with exactly two of the bars and one of the spaces being wide. Any misread that changes the element count invalidates the character. This gave Code 39 a much higher level of base reliability than MSI Plessey. |
Density and Length: Code 39 is not particularly high-density, but it is variable length, allowing it to encode a range of data lengths (up to about 40-50 characters before it becomes too long). MSI Plessey is also variable length, but its binary encoding makes it more error-prone, so for long data strings, the cumulative risk of a misread became unacceptable. While MSI Plessey tried to compensate with check digits, the 'Modulo 10' calculations varied . Some scanners supported different standards (Modulo 10, Modulo 11, etc.), creating compatibility nightmares. Code 39 typically uses a standard Modulo 43 check digit , offering a consistent verification method across different systems. |
Industry Specificity: Code 39 survived because it is used where UPC/EAN is not. It is used for asset tracking, automotive industry labels, and government/military IDs . It is a 'general purpose' barcode. In contrast, MSI Plessey was designed specifically for supermarket shelf labels. When UPC/EAN automated the inventory tracking of those shelf items, the specific utility of MSI Plessey disappeared. |
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The Scars of the Past: MSI Plessey Support Today |
Today, you will be hard-pressed to find an MSI Plessey barcode in a modern supermarket. However, the technology lives on in the digital shadows. Most modern barcode scanners still include support for MSI Plessey as a legacy feature . This is a crucial aspect of scanner design. |
When you program a scanner, you can often enable or disable specific symbologies. For MSI Plessey, the configuration options reveal the paranoia of its users. You can set 'Security Level' to require multiple successful decodes before a single read is accepted, a desperate measure to combat its inherent misread tendency . |
You can also configure the scanner to qualify the length of the code (e.g., 'only read MSI codes that are 8 digits long') . This prevents the scanner from misreading a partial barcode (a 'short scan') from another symbol type. You must also specify which check digit algorithm is being used . Do you verify Modulo 10Or Modulo 10 and 10 (the 'Double Modulo 10' standard)If you set the wrong check digit algorithm, the scanner will not read the code. |
All these configuration options are necessary because the standard was never fully unified. It became a patchwork of modifications. This fragmentation is a hallmark of a defunct technology. Today, MSI Plessey support in scanners is akin to the 5.25-inch floppy drive support in a modern PC: present for backward compatibility, but dusty and rarely used. |
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Contemporary Sightings: Where Is It Still Used |
Searching for MSI Plessey today is like searching for a payphone. They are there, but you have to look hard. |
Legacy Systems: The most common place to find MSI Plessey is in closed-loop legacy systems. A company that invested heavily in a custom inventory system in the 1980s may have never upgraded the hardware or software because the system is 'still working.' You might find MSI Plessey barcodes on storage racks in an old warehouse, on equipment labels in a factory, or in the back room of a small, independent hardware store that never updated its POS system. |
Software Compatibility: The abundance of support for MSI Plessey in barcode generation libraries (like ActivePDF, Atalasoft, FastReports, etc.) indicates that developers are still anticipating the need to create these codes. Usually, this is for data migration or updating old systems where the new software must print labels that the old hardware can still read. |
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The Legacy: Lessons in Standardization |
The story of MSI Plessey is a powerful lesson in the importance of standardization. It is a case study in how technology is not just about engineering but about ecosystem. You can have a technically workable solution, but if it is not part of a larger, reliable infrastructure, it will eventually be replaced. |
The lessons from MSI Plessey can be summarized as follows: |
1. Scalability Over Singularity: A system designed only for the shelf will be replaced by a system that covers the entire supply chain (manufacturer to checkout). |
2. Reliability is Paramount: In the world of 1D barcodes, speed is only useful if accuracy is assured. A code that requires high security settings and double-check digits to function is a flawed code. |
3. The Network Effect: UPC/EAN succeeded because all parties adopted it. A retailer using MSI Plessey was an island in a sea of UPC. It is cheaper and easier to align with the global standard than to maintain a proprietary or niche system. |
The 'variations' of Plessey---Anker, Telxon, etc.---further illustrate this fragmentation . While the original Plessey Code could encode hexadecimal (0-F), MSI changed to numeric only. Different companies had different check digit calculations. This divergence made interoperability a nightmare. When the UPC/EAN juggernaut arrived with a clean, rigid, global specification, the messy, diversified family of Plessey codes crumbled. |
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Conclusion: A Relic of a Pre-Standard World |
MSI Plessey is a footnote in the history of automatic identification. It was a pioneer, one of the first barcodes to see significant commercial use, but it was built on a foundation of sand. Its simple binary encoding, while a virtue for early printers, was a curse for accuracy . Its limited numeric character set made it inflexible. The lack of self-checking made it a liability. When industry standards like UPC and EAN emerged to handle the Point-of-Sale and inventory synchronization, MSI Plessey had no place. |
It persists today only as a ghost in the machine. The fact that your modern scanner can still read it is a testament to the conservative nature of industrial hardware development, where backward compatibility is king. But in the active world of retail, logistics, and manufacturing, the reign of MSI Plessey is over. It serves as a reminder that while a technology might be 'good enough' for a specific problem, global systems require universal standards. The next time you see a tidy, perfectly printed UPC code on a shampoo bottle, remember that before the world had order, there was the wild west of barcodes, and MSI Plessey was the sheriff of the shelf---until a better sheriff came to town. |
cs@easiersoft.com