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The primary aim is to discuss printers, but the printer tends to be an integral part of a cash register. Even if the printer(s) are separate they have an impact on how software works and what it can do.
Point of Sale Evolution
The cash register was invented by James "Jake" Ritty in 1879. Ritty owned a saloon in Dayton, Ohio and the idea of "Ritty's Incorruptible Cashier" was to stop pilfering. Initially the company did not prosper and it was sold a couple of times. John H. Patterson took over in 1884 and renamed the business the "National Cash Register Company". Machines made by the likes of NCR and Burroughs were one of several foundations of the computer industry. Cash registers were also one of the earliest machines with a built-in printer.
The basic idea is to record the details of a transaction - perhaps by making two copies of a paper record.
The customer gets a receipt, which proves that they have paid for the goods. In a small shop this may be somewhat redundant although people have come to rather expect it. The receipt can be vital if the goods are the kind that might be returned. Receipts help make operations like department stores practical - if there were a need to challenge customer honesty those with receipts could prove they had paid.
Of course the shop staff might try to bypass the cash register and sell something for £10 simply pocketing the customers money. This is apparently the origin of penny-off pricing. Price the item at £9.99 and the till has to be opened to give the customer the penny change.
Two-part paper can be a help in transactions - there is a top copy record to give to the customer and a carbon copy wound on a roll as a record. The traditional cash register uses this approach as a check on shop assistant honesty. Transactions shown on the roll should tally with what is in the till, minus the "float". The transactions shown should tally with the stock.
To make a multi-part print a modern cash register normally uses a dot-matrix mechanism. Some cash registers still use a drum printer (which makes a characteristic "whirr kerplunk" noise and has rather nice looking print).
Cash registers may have some elaborations, noise being one of them. When the assistant uses the till some old devices rang a chime, letting the shopkeeper know that money was changing hands. Modern devices tend to be mute, but the cash draw has a solenoid release so it only opens during a transaction and is supposed to be shut at other times. Any deficit in the cash can only be the assistant, since they are the only ones with access to the draw. All sorts of patented inventions made the cash register market quite interesting and competitive.
Until the 1970s cash registers were mechanical - later models usually had an electric motor to activate the mechanism. In the 1970s integrated circuits took over the calculating role and by the 1980s the cash register had effectively become a microprocessor based printing calculator with big buttons.
Using a microprocessor heart obviously gave rise to a new round of invention; machines could be tailored for general dealers, garage forecourt or "hospitality" - hotels, restaurants and pubs. Machines could be networked, sharing a stock database and linking them to the corporate computer system.
Standards began to emerge in the microprocessor world in the 1980s, particularly the emergence of PC architecture and low cost clone boards. This begged a question - can a cash register just be another PC? Traditionally a cash-register has looked rather different, but the differences are largely a matter of keyboard, display and printer. As society gains PC skills generally then the alphanumeric PC keyboard might seem preferable. A multitasking windows operating system might raise cost and reliability issues
Today's "Point of Sale" devices adopt a few rather different patterns:
| Cash Registers - machines intended to stand alone and record transactions without too much other complexity. Simple machines still have a market but feature creep has made machines so complicated that many smaller shops just don't bother with a machine at all. |
| Point of Sale Terminals - machinesbuilt specifically for the job but intended to relay information to a central system. |
| Retail-oriented business systems - a PC that looks like a cash-register and has it's functionality but can do other things - like email and supporting a web-site. |
These machines can look pretty similar and in fact recent models of either tend to be PCs or some kind. There are some points where ordinary PCs, cash registers and POS systems differ. One is software - a crashing spreadsheet is an annoyance, a crashing cash-register is a catastrophe. Another is attachments - cash registers tend to have different screens, keyboards and barcode scanners. Printers are yet another point of departure. Where most of the world wants page-printing: the retailer and customer are used to printing on a narrow till- roll.
Printing & Paper
The innards of a mechanical cash register demanded a particular kind of paper. Usually this is a roll somehwere between 25 and 100mm wide and it might be 1, 2 or 3 part paper. Printing from a roll of paper used to be quite common: teletypes, adding machines and data recorders tended to use a roll, so did train, bus and cinema ticket machines although their rolls tended to have tear-off perforations.
The narrow rolls of paper used in retail cash registers don't find much other application - other calculating devices and weighing machines perhaps. Originally cash registers just printed prices - perhaps with a department or product group symbol so the cashier could get some idea what activities generated turnover. Till rolls originally weren't very wide because even a six-figure price doesn't need an inch of print. In recent times POS terminals have access to a database of products that can be looked up by barcode so most machines provide a wider print - typically 15 to 30 characters for the product description and about 40 altogether. Modern printers are graphical and have a pagewidth of about 1000 pixels, so they can print large text and logos- even the stores phone and website details.
Roll feed makes sense because the retailer can only guess how many items any customer will buy. Even in a supermarket many customers just buy one or two things, most buy a few dozen and the odd few buy hundreds. Sheet feed or fanfold paper would lead to waste. In fact in ordinary printing of e-mail, photographs or bank statements sheet fed paper does lead to waste - its just that in those applications the customer expects a neat, fileable piece of A4 or letter. With a cash register both shopkeeper and customer expect a slip of paper with a column of figures, total, tender and change.
As always happens with printers, cash register paper became a potential profit centre for manufacturers. Make a printer that takes a specific width of paper or a different kind of spool and nothing else will do. Manufacturers still sometimes lock retailers into a specific stationery, for instance with a formulation for two-colour thermal paper. These days the most likely consumable to appear in proprietary cartridge form is impact printer ribbon.
In the mechanical cash register the printer was a great part of the machine. In electronic registers the printer subsystem can easily be electrically separable - its just a "port" on the system. System designers have often taken advantage of the flexibility, making the printer something that is stand-alone and can be placed anywhere in a workstation. Some designs that look like conventional cash-registers want an internal printer so they might use a "print engine" - a chassis that can be incorporated into other equipment manufacturers designs.
Print technologies for cash registers tend to focus on thermal and dot-matrix impact printers. There is no technical limit that says inkjets and laser printers can't work - but there don't seem to be any 150mm pagewidth laser-printers and
a 210mm mechanism (for A4 / letter / legal) tends to be too big
transaction printing processes don't have a fixed page length - but most laser printers do
traditional cash-handling processes value a carbon-copy which inkjet and laser printers can't do
Cash registers are aimed at smaller shops and do what is traditionally expected - calculate the sale, record the money and open a cash drawer. The cash-register is usually intended as a stand-alone device. Today's machines may well record the transactions on two part paper (receipt and till roll) but will also maintain totals in memory so "cashing-up" - checking that the till holds what it is supposed to - is just a matter of turning the control key to the supervisor position and getting the total. Features like password protection for the cash drawer improve security.
Older cash registers tend to use proprietary circuit boards and parts. During the 1990s there was an increasing move to use standard PC components. At first the main problem was to shrink the PC to a reasonable size and hook it up to a shop-oriented keyboard, display and cash drawer. There are few problems packing a PC into the space now. Standard mass produced PC parts tend to be less expensive than proprietary electronics, however there are a few issues.
The PC user interface isn't appropriate -generally the aim is to enter actions and products with a single keypress or a barcode reader rather than with a mouse action. Ordinary PC keyboards don't seem really right for the job either. Tills didn't traditionally expect typing skills, they had either more keys and a product per key, or fewer keys for just recording the price.
Program(s) and how to launch them - the program is proably too complicated to be held in the PC boot ROM or flash and probably does need the disk - but it doesn't really need a multitasking windowed operating system. Microsoft DOS was popular - all it did was launch a proprietary program. Recent devices tend to use an embedded small-footprint board - quite possibly running Linux from flash memory.
Screens used to pose a problem - A CRT was usually far too large and there was a special market for 5 and 9 inch CRTs. Today's smaller VGA flat-screens are fine for POS use - although the trend to bigger flat screens could e-create a market for special small form-factor devices.
cash drawer may still be problems.
Printer mechanisms for a cash register have traditionally been built into the chassis of the machine. A single neat unit is what shopkeepers expect and gives security that no-one can tamper with what the machine is supposed to do. Printers in tills from smaller manufacturers are likely to be "engines" from one of the larger printer manufacturers (Epson for instance) but that probably won't be self-evident.
Cash-registers fundamentally have to do the old job of recording things without too much complexity or possibility of error. All the features PC software can add are nice - but not if they confuse things for the shopkeeper. Whilst it might be great to have comma-delimited data downloaded to a flash-pen ready for loading into Excel there is still a demand for a till-roll and the best way to print receipt and roll at the same time is to feed two-part paper through a dot matrix printer.
The till-roll printer needs some special fittings like:
| a tear-off bar or better still a guillotine for the receipt |
| a take-up reel for the till-roll |
| a paper-low switch so that the roll doesn't run out in the middle of a transaction. |
In principle any printer can be used for cash-register applications although a newsagent or sweet-shop that laser-prints a receipt would seem a bit odd. Printers designed for retail tend to take norrow, roll-fed paper and do a couple of odd things. One feature is that POS printers respond to the <bell> signal (ctrl-G or ASCII-7) by closing a switch which releases a cash drawer.
Point of Sale Terminals can take a rather different form. In fact a POS terminal may have no very fixed form at all, its usually part of a chekout or retail workstation with a moving belt and bagging area. There might be one or two screens - one for the operator, another for the shopper - not necessarily with the same message. There will certainly be a barcode scanner - on more expensive systems this is embedded in the workstation. Unfortunately barcodes don't always read well so there will be a keyboard as well - at least a numeric field, usually much more. Cash drawers are still the basis of security. Optional extras are weighing machines and keyboards with a labelable key per product. There will certainly be a printer, but it's likely to be a stand-alone model.
As the name implies the device is primarily a "terminal" working to a server of some kind. Outside the retail world terminals are generally dumb input and output devices largely replaced by semi-independent desktop computers. The POS terminal is primarily a data collector - it doesn't necessarily have to receive much data from a server.
Although the POS terminal is not intended to work alone given that a network is an innevitable weak point POS terminals can benefit by having the ability to store data locally then relay it to the server when convenient. To do this the product data (EAN code, description) has to be downloaded into the till
Till-rolls are one of the commonest low speed print jobs. Low speed is a comparative term - at the point of sale the shop assistant scans or keys in the details for the goods and the cash register prints out the list and the total immediately, nobody wants to be kept waiting.
Reliability is a high priority - a cash register that won't print the receipt is annoying even if it can still record the information in memory. Any break with standard practice leaves the customer vaguely dissatisfied.
Credit card transactions in smaller stores often use a seperate machine to record transactions - the printing priorities are the same, instant production of a record.
Single part print will often be adequate where the and if so it is normal to use thermal direct printing. Advantages of thermal print in this role are:
Simplicity - it is easy to load a roll of paper, which just clamps between printhead and feed roller. Material is usually in rolls because there is no way of knowing whether the customer will buy one item or 100 items, so the output is produced in whatever length is appropriate.
Speed - thermal print at about 4 inches per second is more than sufficient to keep pace with even the fastest data input.
Notice of failure - there is only one consumable, the till roll. Till rolls commonly have a pink end strip so that the operator can change roll at the next customer.
Printhead failure could be sudden but rarely is. More usually the printhead loses one dot-position. Loss of one dot is usually a prelude to wider failure but at 203dpi doesn't completely wreck readability.
Till rolls tend to come in standard widths up to about 78mm (3.1 inches). Small print is acceptable, but at most this sort of material can hold about 40 characters across. This is enough for product code and / or very brief descriptions together with price.