How do barcodes work?
For a quick understanding, think of bar codes as visual Morse Code. Digital “1’s” and “0’s” are printed as the dashes and dots of a special Morse Code. If you look at a very thin slice of barcode, you’ll see wide and narrow bars. In reading the barcode, the scanner’s red beam is absorbed by the dark areas of the bars and reflected by the light areas between bars. A photo sensor (in the same scanner that throws the light), sees the reflected or absorbed pulses of light created as the light moves across the code. Long and short light pulses are sensed and reassembled into the same bits and bytes that produced the printed code, or Symbol, in the first place.
What's all this about step ladder and picket fence barcodes?
These terms refer to the direction in which a barcode is presented for scanning. If the code runs up and down so its bars resemble the rungs of a tiny ladder, that’s “step ladder” barcode. If the code runs left and right the bars resemble a little picket fence, hence the term. This stuff is especially important in unattended scanning where for example boxes are rushing past a fixed scanner mounted on a conveyor line. There is often confusion about step ladder or picket fence orientation when printing bar codes on roll of fan fold label stock. If the code is printed so that the bars come out of a printer parallel to the print head they are referred to as step ladder. If they are perpendicular to the print head they are considered picket fence. It’s really only important when using thermal transfer or dot matrix printers. On these printers the best quality code is generally printed picket fence. It’s really best to talk about bar code print orientations as drag or step printing. What most people would call picket, as described above is drag mode. A bar is printed the paper steps forward the next bar is printed. In printing the ladder mode described above is cleaner. The printer activates all the little dots needed to print an entire code and then drags the paper past the active dots. Drag mode is a higher quality print technique.
How do I figure out how tall to make my barcodes in relation to their width?
Who cares? No, really it does matter. In theory, your barcodes only have to be as tall as the thickness of your scanner’s beam. But try to line that beam up with something that looks like micro-Morse Code and you’ll be scanning all day! Each tiny slice (across the bars) of your barcode has the same pattern and data. But, you want to make your symbols tall enough to be “shot” without being too fussy about your aim. The longer the code, the tougher it is to get the scanner across all the bars without tilting it and missing a few bars at either end. Miss any bars your scanner won’t read. (This is an all or nothing business, this barcode biz is.) (See: Start/Stop Characters). So make your codes tall enough to be scanned easily at slight angles. Some gurus like a symbol’s height to be one-third of its length. Do what makes sense for your label size and shape, but in general, the longer the code, the taller it should be. Look at some of the codes you see on shipping cartons; often they’re taller that they are wide. That’s to allow all kinds of crazy scanning angles.
How do I print barcodes?
Barcodes can be printed on your product’s packaging, or produced as add-on labels. Labels can be preprinted or produced on demand. Bar code labels are most commonly printed using PC based software packages and are printed using dedicated barcode printers. Companies such as Data Support, Inc. are experts in specifying the components you will need. On demand printers for barcoding are usually “thermal transfer” printers. Thermal transfer printers use a heat producing print head to melt ink carried on a thin plastic ribbon. The ink is transferred to the label stock as it moves through the printer. These tiny, square ink dots produce the bar code and text images on the label. The images are printed rapidly and are quite durable. Special stock and ribbons can be used to produce very durable labels made of paper, plastic, and even metal foils. Some thermal printers use heat sensitive label stock and do away with the ribbon. Most Thermal Transfer Ribbon (TTR) printers can be used without a ribbon using “direct thermal” stocks. Direct thermal stocks are not suitable if labels will be exposed to higher temperatures or if they must last a long time. All sorts of adhesives are available for all types of uses, come to us with your particular needs.
What are quiet zones?
Barcodes are scanned using reflected light (see: How Do Barcodes Work?). If you shine your scanner at a page of printed text, the patterns it will see will be all sorts of black and white gibberish. A scanner needs a little “quiet time” just before and just after passing through a scanned symbol. That’s just to make sure the light patterns the scanner sees are barcode bars and not those tiny bits of black and white text from the Daily News. The scanner wants some blank white space before and after the barcode so it can be sure it has scanned a valid pattern. The quiet zones need to be at least 10 times the width of the skinniest bar in the barcode (see: How are Barcode Parameters Specified?) Therefore, symbols printed with fatter bars need bigger quiet zones. So, be careful of printing your codes too close to text, lines, or the edge of your forms or labels. (Just to be clear, the quiet zones are required on sides of the codes in the direction of the scan. Empty space is not as critical at the tips of the bars.)
License Plate barcodes, what does that mean?
No, that’s not bar coding for the Motor Vehicle Office. Bar codes are often used to tell a computer to look up more information. Your bar coded part number “74701” may be a black stapler. You know that it’s the manual desk model. The computer at the store knows a “74701” costs $12.95 in their price lookup file. The term comes from the concept of a car’s license plate. When a trooper pulls you over and runs your plate number, the license plate keys a database of all kinds of information, “So you have seven outstanding warrants eh?” Most bar codes are used this way.
What are Start/Stop Characters?
All bar codes use a few bars at the beginning and end of the code to say, “This is the beginning of the code, and this is the end of the code”. It’s kind of like putting your information in parenthesis: (DATA). If a scanner sees START CODE-DATA-STOP CODE, the whole code has been scanned. You wouldn’t want to scan 123456789 and get only 1234 on your scanner would you? (NO you wouldn’t!). That’s what start/stop characters prevent. In code 39, for example, the data is always coded as *DATA*, even though you don’t often see the *’s printed. Your bar code software or printer will automatically add stop/stop characters for you; you don’t need to key them in. Start/Stop characters have another important function in some cases. The bar code parameters specified, Symbology). Therefore, a scanner can figure out which symbology is being scanned at any given time. Most scanners are “multilingual” and the start/stop characters are the key to the “language” being scanned.
What bar code symbology should I use?
Quite often, the symbology you use will be pre-determined by your clients or industry. Selling product in a retail store? UPC on each unit will be scanned at the cash registers. Shipping master cartons to that same retailer? Code 128 labels on the outside are related to your EDI Advance ship notice. For your own in-house labeling, say for warehouse inventory, use a symbology that supports your data. Code 39 is very common for any alphanumeric data and can be printed and scanned almost universally. So is Code 128. If your bar code data is (and always will be) only numeric, Interleaved 2 of 5 may be for you. Talk to your guru (we’re good at this), or obey your master (yes Mr. Wal-Mart, anything you say!)
Can I print bar codes in color or print codes on colored backgrounds?
Yes… and no. Remember, bar codes work with reflected light (See: How do Bar Codes Work). A black code on a white background is always best. Black absorbs almost all red light; white reflects almost all of it. Nice contrast for the scanner to read. Put that same black bar code on a green background and you’ll have a tough time scanning. You see, green looks green to your eye because it soaks up all of the colors of “white” light and only bounces back the green part of the light. (Remember that all the colors of the rainbow are in white light.) So…, red light gets sucked-up by the black bars and sucked-up by the green background. Blam-dead air, or no “print contrast” as they say in the bar code biz (see: Print Contrast Signal “PCS”). Now, print your code in red on a white background. Red bars reflect red light, so do white spaces. Blam- again, no “print contrast”, same result. By now you can tell that a green code on a white background would work- white reflecting and green absorbing your scanner’s beam. Beep goes the scanner! Now, do you feel like working? How the heck does those white and shiny silver codes on the side of your Coors can work – I must be lying, right?
What are 2-D Symbologies?
You know, everyone wants more all the time. Ordinary or “linear” bar codes are used to code a number or other short pieces of data (See: “License Plate” bar codes). That’s OK if you only need to convey a small amount of information about your product. For example a UPC code tells both you and that retailer that this item is “Campbell’s 8-ounce beans” (See: “How do I get a UPC Number). Many applications need to code more extensive information than that, maybe even hundreds or thousands of digits or text. Printing and scanning of such data requires 2-D symbols. 2-D symbols code data both horizontally and vertically. That’s why their called 2-D, short for 2 Dimensional. They tend to look like squares full of chopped bar code lines. “2-D bar codes” are really a misnomer, but you hear it a lot. (Don’t go around correcting people, nobody likes a wise guy). Depending on the symbology, lots of data can be packed into a small space-the Gettysburg Address in a square inch sort of thing. Common 2-D codes are PDF 417, Data Matrix and Maxi Code. Most bar code printers can print 2-D codes, but special scanners are required for reading the codes.
How do I get a UPC number and how do I use UPC?
UPC numbers, used in retail sales, have two pieces of information. The first part of a UPC code is a number which identifies your company; “Ed’s Freeze Dried Omelets, Inc.” the second part of your UPC number represents your product code, “Western omelet with Goat Cheese Sauce”. The whole world needs to know that your company, “Ed’s” is number “012345”. That way, no one will confuse “Ed’s Freeze Dried Omelets” with “Goodyear Tires” I hope! A governing body, the Uniform Code Council or UCC manages the assignment of company numbers. To get a company number, you must register with the UCC and pay a nominal fee. Fees are assessed on a sliding scale dependent on your annual sales.