We have all seen them. Many of us have used them. I'm talking about Point Of Sale terminals or POS systems. From old-style mechanical cash registers to modern wireless-electronic customized PDAs, POS systems are tightly integrated into our society and way of life.
It's gotten to the point where a POS system can make or break their owners. We have all been on line at a checkout counter somewhere while some minimally trained cashier struggles with her POS system to ring in every purchase. We all know the frustration of waiting in line while a cashier enters in skew numbers that don't work, scan bar codes that don't work, or wrestle with a machine that's not doing what the cashier wants it to do.
Figure 1: Traditional checkout counters are simplified with smaller and less expensive scanners that look for barcodes at multiple angles. These devices drastically reduce the costs associated with conveyor-belt types of scanners.
When new stores open up with faster and more efficient POS systems, this is a definite factor in deciding where to shop. I have made a decision where to buy things based on multiple experiences waiting on line while antiquated POS systems burn up my time.
The intelligence and integration of a POS system is also important. Large stores and supermarkets, for example, will run many sales and specials and, if a system is not properly integrated, non-sale prices ring up. This is a turnoff to customers as well who feel their trust has been violated.
Figure 2: POS systems are moving from fixed checkout locations to personal POS systems that you carry along with you while you shop. With the device shown, you scan items as you put them in your cart.
From network globalism to iso-synchronization, the movement these days is toward making everything play by a distinct set of rules. The lonely little POS terminal is not immune from these pressures. POS systems are undergoing transitions as they migrate from simple transaction recorders to tightly integrated parts of a corporate whole. True, small mom-and-pop shops can still get by adequately using nothing more than a mechanical cash register. However, more advanced franchises, stores, outlets, and service industries are pushing this technology into other areas such as inventory management, JIT (just-in-time) delivery, and global logistics.
At the core of any POS system is embedded intelligence along with the I/O and accumulation functions (Figure 3 ). After all, the main function is to interact with an operator to input a transaction, record it, keep accumulated sums, and issue receipts. Like an onion, functionality is layered around the core. It's not rocket science. You pick the peripheral pieces you need to fulfill the tasks at hand, sort of like choosing dishes from a Chinese menu.
The functionality onion does get more complicated when it comes to communications. Here, similar tasks may opt to use different methods of communications. Modular approaches are best used for this task. Finally comes the ever-present fringe. If you expand the definition of POS to include anything that processes input to make a decision and post a transaction, this greatly expands the application of the same core technology. For example, POS terminals would now include inventory-management hand-held devices, delivery terminals, security and entry terminals, and even digital wallets.
While the technology at the fringe of the onion may seem “out there”, progress is being made on all fronts.
A key decision is to make up-front is how smart is the core? There are architectural tradeoffs that translate into cost and performance ramifications. A dumber terminal will simply record a transaction and pass it along. A smarter terminal will do more processing and is usually more independent of constant communications with a central or distributed host.
Dumber terminals cost less, use less power, and are typically easier to use. On the down side, they depend on external smarts to accept transaction information, do processing, and send back results. Heavily burdened networks will see performance delays.
Smarter terminals are more complex and will almost always require customization of the interfaces and dataflows, For example, these terminals may be loaded with tablesthey may breakdown a transaction and post specific information to different machines and departments on the network. A dumber core may be harder to interface with new I/O devices and communications protocols but, then again, could be cheap enough to replace.
Ultimately, the decision here will influence the behavior downstream. As with any system design, the needs will determine the end architecture. Here is where you balance. You don't want to limit a design too much; on the other hand, you don't want to kill ants with atom bombs.
I/O is where the fun is. There are typically several, somewhat redundant I/O devices in most systems. For example, at a grocery-store checkout counter, there is usually a display for the operators as well as the customer. There will be a keypad for the operator and, often times, a small keypad for a customer to use with a debit or credit card. Similarly, there may be a main embedded printer on the operator's interface as well as a customer receipt printer.
For lowest cost, POS terminals will use membrane style keyboards. These are cheap, durable, and can be made with nice graphics to simplify use. Elastomeric and rubberized keypads fit into this category as well. Old metal domes have given way to Poly-Domes that can take a puncture and keep on working. What's more, the ability to embed LEDs within a membrane helps provide feedback and indicates mode and status. There are tooling and NRE costs with this approach and ESD issues must be addressed, but this is still an effective and low-cost way to go, especially when you need many input buttons.
Displays and touch screens are in widespread use as well. While more costly and more sophisticated a design (usually using an embedded PC or similar processing), these components provide a fast and sexy way to input information and interact with the system. Generally speaking, while CRTs are the most inexpensive display devices, most POS systems have switched to LCDs. These displays are smaller, lighter, use less power, generate less heat, and don't have high-voltages accessible to spills and moisture. Monochrome LCDs are cheaper than color units and can be transflective, meaning they can use both backlighting or reflected ambient light.
Color TFTs are the most expensive displays and are not transflective. Brightness issues can play a role here if the units are to be used outside or in very brightly lit areas. There is progress being made on transflective TFTs. but the technology is far from mainstream. TFTs are the nicest looking displays and operator eyestrain can be significantly reduced through the use of clear but soft coloring.
With both monochrome and color LCDs, viewing-angle limitations are usually not an issueoperators tend to use them these displays with a low viewing angle. POS terminals may use plasma or vacuum fluorescent displays alphanumeric information if the application requires a wide viewing angle.
There are a wide variety of technologies to choose for printer terminals, but the dominant technology to date is dot-matrix impact. Some thermal printers are still in use, but are declining due to the poor quality of the output. The same holds true for electrostatic printers which, for the most part, have faded away.
Depending on what type of POS system you are designing, a variety of other I/Os will need to be present. Most common are magnetic-strip readers for credit cards and debit cards. These can be made or obtained from OEM vendors fairly cheaply. Also very common are barcode readers. These can be made or obtained from OEM vendors as well. Bar-code readers range from wands to systems mounted in a conveyor such as those found at a supermarket.
Not yet too common yet in the U.S. are smart card readers. These readers tend to be more sophisticated and costly since they require encryption, decryption, and processing. Also, smart card readers must be flexible and powerful enough to support old, present, and future flavors of smart cards, which are changing quite rapidly as hackers keep breaking card security.
You will often find external and modular units in POS systems that combine I/O devices. One case in point is a combination card reader, dialer, modem, and small alphanumeric display. We've all seen these devices swipe our cards, punch keys, view verification information, and print receipts. Another device that is becoming more common is the signature pad. For this device, a combined display and touch screen reads in, displays, analyzes, and stores digital representations of your signature.
As you can see, many peripherals will plug in to each other or a local central controller to play together. Just for local workings, several independent I/O levels and protocols may be used. However, a POS is not an island unto itself any morethis is where high-level communications comes in.
More reliable and lower cost communications options have driven POS interconnectivity. Older, slower, and distance-limited proprietary and RS standards-based designs have given way to token ring- and Ethernet-based topologies. These topologies provide higher speed, low cost, and a modular networking approach.
Wireless is in use in the service industry but far behind where it could be for public-interaction applications. In many parts of Europe, for example, it is not uncommon for a waiter to take your order on a wireless PDA-like device that instantly informs the kitchen to start cooking, automatically updates billing, and lets the waiter know when the food is ready. We in the U.S. are slow to adopt wireless for many applications, but that may change. Recent problems between overlapping standards such as Bluetooth and 802.11 have been solved. Lower-cost, lower-bandwidth RF modules are approaching the $5 per link range, making these modules available as on-board options.
However, progress is being made in the States. Retailers are seeing the benefit of having a wireless POS terminal they can wheel out and open up during busy times. These retailers are also realizing that the space savings from more compact wireless terminals give them more room for merchandise in display cases, including “impulse buying” items.
Ethernet is the key these days for most wired applications. The huge PC-driven market has resulted in low-cost Ethernet for everything. Additional advantages for this technology are hop distances in kilometers and speed grades of 10Mb/s, 100 Mb/s, and 1Gb/s, which are fast enough for even the most aggressive POS systems.
Well-established standards and industry interoperability are very appealing and designers have a wide choice of discrete functions like MACs and PHYs, as well as for integrated single-chip solutions. Also spurring the acceptance are the low-cost switches and routers to support the data-flow infrastructure.
This relieves POS designers of the big burden of not having to design all proprietary pieces of the puzzle. It also permits access to the Worldwide Web. Web access can be a good or a bad thing, hinging on the robustness of your design. Some industry visionaries see the future need to check email at the gas pump or to get restock requests from your refrigerator.
Security is of foremost concern. Ethernet and Internet are not very secure. There is enough expertise out there to permit medium-skilled hackers to really interfere with the workings of a POS system. These problems are being solved as more secure tunneling and VPN isolation practices are employed. The same problems can be solved on the LAN side by using fiber optics as the interconnect medium. This pretty much solves local security issues from outside predators. This won't solve insider security issues or outside hackers if you are globally connected, however.
Prices are dropping as x4, x8, and x12 fiber arrays are deploying. Small and modular VCSEL Transmitters and Trans-Impedance Amplifier (TIAs) Receiver arrays offer fanned-out point-to-point secure communications links. For most applications, this is overkill and much more expensive than low-cost wired or medium-cost wireless medium solutions. But, when high security is a must, this is a viable optionit's still too much of a cost burden for the rest of us.
Wired and wireless security problems will continue to be solved because there are benefits of reaching the next plateau. This is the situation for an isolated POS machine located anywhere is communicating in real time with various local and global headquarters, suppliers, manufacturers, distributors, and so on. While not as important with public POS systems aimed at retail, these features are useful for service industries, such as delivery services like Fed-Ex, UPS, DHL, and the post office. Real-time tracking is critical to the success of these businesses. Oh, and those handheld wireless pads they use to scan, track and enter information? Those are POS systems as well except here the “S” is a Service and the transaction takes place in the field. Vending machines, gas pumps, ATM machines, utility readers, and so on are also types of POS systems that also benefit from real-time information.
Figure 6: Point-of-service units, similar to the one shown, contain the same technology found in point-of-sale systems.
There are fringe technologies that may seem far-fetched, but are worth knowing about. Voice recognition is working rather well for speaker-independent applications, but has not progressed overcome certain levels of speaker dependencies. Voice recognition is not really being pursued for POS applications, since the ambient noise in a typical POS environment could be a factor.
There are fairly low-cost fingerprint scanners, however, and these are being designed into the next generation of digital wallets. The combination of an LCD, touch screen, magnetic stripe writer, and fingerprint reader can create a cash-free wallet that is useless to anyone other than the wallet's owner.
There have already been multichip modules (MCMs) made of DNA processing designs that can be used to positively identify an individual. The current state of nano-technology is sufficient to physically move samples along for processing with micro-miniature, surface-mounted ultraviolet lamps used to illuminate the processed sample. The process takes 20 minutes to do an identification, which is not feasible for any current application. In addition, the cost of such a system is not feasible for real-world use. But, then again, this technology is currently just in the research phases. Who knows how advanced and refined this could become.
The mention of it can bring laughter, fear, praise, condemnation, or disbelief, depending on whom you talk to. I'm talking about implanted transaction processors. As far fetched as this seems, the technology is already offered today, helping to find missing children and pets, and as replacements for dog tags in special-forces circle. There is even a manufacturer's van traversing the country, demonstrating products and enticing people to buy devices.
The technology is advancing to the point where global wireless and audio capabilities will be integrated into this implantable device. There is already talk of giving people free airtime in return for listening to commercials. Something bothers me about becoming a tracked and monitored machine but unfortunately, I see it coming. Like all technology, it marches on and in these days of terrorist, espionage, and the need for security, you never know.