A bar code symbol is made up of alternating lines and spaces. Combining these bars and spaces in specific ways is similar to using Morse code. Using Morse code to spell out SOS uses 3 dots (…) then 3 dashes (—) and then three dots again (…). A bar code is a “machine readable symbol” meaning that it can be decoded (turned back into number and letters) by any of several types of scanner. The bars and spaces are analogous to the dots and dashes.

Using only bars and spaces, a bar code can represent numbers or numbers and letters. When scanned by a laser scanner or imager the bar code returns a signal pattern that is then interpreted by the bar code reader; turning the symbol back into numbers and letters. Using bar code almost any item can be identified – part numbers, location IDs, packing slips, shipping documents, driver licenses – the list is endless.

A “linear” bar code is one dimensional; that is, the information is the same whether you scan across the top, bottom or through the center. There are also 2 dimensional bar codes which included “stacked” (many 1D codes stacked together) and “matrix” (a series of dots or lines. RFID (Radio Frequency Identification) also represents a ‘type’ of bar code. The key to a bar code that is easy to scan is contained within the specifications for that symbology. Bar code specifications are the rules on how the bar code is to be produced. A device called a bar code verifier is basically a scanner with a small integrated computer; when you scan bar code symbols with a verifier it compares what it sees with the built in specifications for that symbol and returns a letter grade. A, B and C are acceptable, D or F are not.

Code 39 is used in many manufacturing operations including the automotive industry; Code 128 encodes information differently and allows more information to be compressed in the same space as a larger Code 39 bar code. UPC is used in retail; I2of5 is called Case Code and is often printed on corrugated boxes. Contact ADC Integrated Systems for detailed information on bar code symbols and printers.

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