The process to convert a computer message into a bar code symbol is a fourstep

Transcription

1 Bar Code Symbologies A bar code symbology is a system for representing data in the bars and spaces of a bar code. A bar code consists of a number of printed bars and intervening spaces. The width of the bars and spaces, as well as the number of each, is determined by the specification for that symbology. The process to convert a computer message into a bar code symbol is a fourstep process: Establish the type of data to be represented and the number of characters in the message. Translate the human-readable information into binary format. The number and value of the binary zeros and ones are determined by the bar code symbology selected. Create the bar/space pattern that represents the binary word used in step 2. Format the individual bar code characters into a symbol that represents the complete message. The complete symbol consists of quiet zones, start and stop character patterns, data characters, and optional check digit characters. The most widely used symbologies are discussed and illustrated in the following pages. Code 39 Code 39 was the first alphanumeric symbology to be developed. In 1981 it was established as the official Department of Defense and the official government symbology standard. The Automotive Industry Action Group and the Health Industry Business Communications Council recommend Code 39 symbology. Also known as Code 3 of 9, it is the code for industrial, medical, electronics, telecommunications, corrugated shipping containers, commercial and government applications. Numbers, letters, symbols, and some punctuation can be encoded in Code 39 bar codes. Capital letters A to Z Numbers 0 to 9 Space character -. $ / + % characters. The name, Code 39, signifies each character is composed of nine elements--five bars and four spaces. Each character has three wide elements and six narrow, each separated by an intercharacter gap. The intercharacter gap contains no information and should be approximately the same size as the narrow element width. For a decoder to distinguish between the wide and narrow elements, a minimum wide to narrow ratio needs to be established. Depending on the resolution used for printing the bar code, the width of the wide element should be at least two times greater than the narrow element. The width of a narrow bar should be the same as a narrow space; and, the width of a wide bar should be the same as a wide space. Code 39 is self-checking, discrete, and utilizes start/stop characters, intercharacter gaps and allows bi-directional scanning. Both the start and stop character for this Last update 6/30/2004 Page 1 of 16

2 symbology is an asterisk (*). Together, the wide elements (represented by "1") and narrow elements (represented by "0") create a pattern that is used to obtain its equivalent numeric value. Full ASCII Code 39 The Full ASCII Code 39 expands standard Code 39 to include the full 128 ASCII character set using the existing Code 39 character set. This is achieved for certain ASCII characters by pairing two Code 39 characters to represent the single ASCII character. As shown in the example, a carriage return (CR, ASCII 13) is encoded using the two Code 39 characters, $ and M. Because Full ASCII Code 39 is derived using standard Code 39 characters, your bar code reader must be configured for Full ASCII Code 39 to properly decode the Full ASCII Code 39 character set. UPC Since 1973, the Universal Product Code (UPC) has been identified with various types of retail industry. However, it can be used in shipping and retail applications. UPC is a coding system as well as a symbology; it is designed to identify a product and its manufacturer. The Universal Product Code Council assigns all UPC codes. The number system character, as shown below, indicates the type of product the bar code is identifying. Number System Character Product Type 0 Regular UPC codes 1 Reserved Last update 6/30/2004 Page 2 of 16

3 2 Random-weight consumer items 3 Drug items 4 In-store marking of non-food items 5 Reserved for coupons 6, 7 100,000 manufacturer identification numbers 8, 9 Reserved for future use UPC is a fixed length, numeric, continuous symbology consisting of two halves which can be read independently. Encodation differs for the left and right halves. Parity refers to whether the sum of the bar module widths in a given character is an even or odd number. The check digit is the last digit and is calculated from all of the other numbers encoded in the bar code. There are four versions of UPC bar code. Two most commonly used types of UPC are Version A, which encodes twelve digits and Version E, which encodes six digits. However, the encodations of all versions are basically the same; the difference is primarily the configuration of the data field. UPC Version A UPC Version A is a numeric, fixed length, continuous bar code. Commonly used for grocery, drug or health-related items, UPC Version A encodes twelve digits; six digits in each half with left, center and right guard bars. Guard bars are usually printed with greater length than other bars in the symbol to maximize the allowable scanning tilt angle and to divide the symbol in half. Last update 6/30/2004 Page 3 of 16

4 Each half is referred to as left parity and right parity and can be decoded separately. Bars and spaces can be one, two, three or four modules wide. Version A has two levels of checking; the first is a parity check of individual characters within the first half; the second is a modulus 10 check digit. The encodation patterns for UPC Version A are different for the left and right parities. UPC Version E UPC Version E is a zero-suppressed version of UPC A used on items often too small to include a bar code. UPC Version E allows manufacturers to encode a limited number of unique twelve digit product codes into eight digits. UPC Version E is a numeric, continuous, fixed length bar code. The eight-digit code consists of a number system character (0), a three-digit manufacturer's code, a three-digit product code, and a check digit. UPC-E Version 0 automatically includes a zero in the number system position; UPC-E Version 1 includes a one. The Universal Code Council as listed below establishes guidelines for manufacturers to properly code products. Last 3 Digits of Manufacturer's Available Product Code Last update 6/30/2004 Page 4 of 16

5 Mfg's Code Number Item Numbers Number 3 000, 100, 200 1, , 400, 500, 600, 700, 800, , 20, 30, 40, 50, 60, 70, 80, 90 Manufacturer's number does not end in zero EAN European Article Numbering system also known as the World Product Code (WPC), and the International Article Numbering Association (IAN or EAN), is a symbology developed for international businesses. EAN has two versions, EAN 8 and EAN 13, which are variations of the original UPC coding system developed in the United States. Both versions are fixed length, discrete and numeric bar codes. The first two digits of an EAN bar code are the country code. Country codes 00, 01, 03, 04, and are assigned to the United States for compatibility with UPC. An EAN scanner can decode UPC; however, the reverse is not necessarily true. The EAN 13 symbology contains the same number of digits as UPC Version A except it includes an additional digit representing a country code. Except "0", character set patterns for the left half of EAN 13 are the reverse of UPC Version E. When calculating the check digit, EAN 13 ignores the leftmost digit and calculates the check digit in the same manner as UPC-A. Last update 6/30/2004 Page 5 of 16

6 The EAN 8 symbology is divided into left (odd parity) and right (even parity) halves. It has left and right guard bars and eight digits including a modulus 10 check digit and is structured like UPC Version A symbology except that four digits are encoded in each half. Bookland EAN Bookland EAN follows the same guidelines as an EAN 13 bar code and in addition, contains the ISBN (International Standard Book Number). Bookland EAN bar codes always begin with 978. Interleaved 2 of 5 Interleaved 2 of 5 is a high density, continuous, numeric, self-checking, bi-directional symbology used in warehousing, product or container identification, airline ticketing, baggage and cargo handling, industrial and automotive applications. The following figure details an Interleaved 2 of 5 bar code, for example, The adjacent characters are interlaced (interleaved) alternating the spaces from one character with the bars of the other. Interleaved 2 of 5 bar code encodes two digits; one in the bars and one in the spaces and requires an even number of digits to encode information. All of the even positioned data is encoded in the spaces; and, all of the odd positioned data is encoded in the bars. If the encoded data has an odd number of characters, you must add a leading zero (0). Last update 6/30/2004 Page 6 of 16

7 There are two wide bars and three narrow--five spaces in each character, two are wide and three are narrow. A complete Interleaved 2 of 5 bar code consists of a start code (two narrow bars and two narrow spaces), data characters, and a stop code (a wide bar, a narrow space and a narrow bar). It may also contain an optional check digit Code 128 Introduced in 1981 and widely used in general industrial, retail container labeling and inventory, Code 128 is a high density bar code and represents the Full 128 ASCII Character Set. It is a variable length, continuous, bi-directional, alphanumeric symbology originally designed to encode multiple identification into a compact alphanumeric bar code. Each character consists of three bars and three spaces and an overall length of eleven modules (either black or white). Bars and spaces can either be one, two, three, or four modules wide. Last update 6/30/2004 Page 7 of 16

8 The character set consists of 103 different characters, three start characters and one unique stop character. With use of a function code, (FNC 1, FNC 2, FNC 3, FNC 4), Code 128 offers a concatenation feature, and has the ability to decode and transmit several messages as one. The function code determines instructions for the bar code reader as follows: FNC Characters FNC1 FNC2 FNC3 FNC4 Description Reserved for future use or special applications such as UCC-128 shipping container code. Special instruction for bar code reader to temporarily store data (append) from the symbol containing the FNC 2 character and transmit it together with the next symbol character. Reserved for bar code reader initialization and other special bar code reader functions. Reserved for future use or special applications. UCC-128 Serial Shipping Container Code (Mod 10) UCC-128 Mod 10 is a subset of Code 128 and is a twenty-two character, alphanumeric, continuous, fixed bar code, used primarily on shipping containers. Every bar code starts with a Start C code followed by a function code (FNC1), pertinent data characters (19 digits), modulus 10 check digit, modulus 103 check digit and stop code. Start C code, together with the function code, forms the overall UCC start code notifying the scanner that a specific UCC-128 bar code follows. The two-digit qualifier code distinguishes it from other UCC and EAN codes. The one digit code identifies the type of serialized shipping container package. UCC/EAN approved valid packaging values are listed below: Shipping Container ID Number Description 0 Serial number shipping case or carton ID 1 Serial pallet (larger than case/carton) Last update 6/30/2004 Page 8 of 16

9 2 Serial container (larger than a pallet) 3 Undefined packaging type 4 Inter-company defined shipping container code 5 Mutually defined between trading partners 6-9 Reserved for future use A six-digit UPC manufacturer number together with an additional zero completes the seven-digit manufacturer's identification number and is assigned by the UCC/EAN. The Shipping Container Serial Number Identifier individually identifies each shipping container packaged by a provider. Codabar Developed in 1972 and commonly used in libraries, blood banks, air parcel carriers, photofinishing envelopes and the medical industry, Codabar is a numeric, bidirectional, variable length, discrete, self-checking bar code symbology. In 1977, the Committee for Commonality in Blood Banking Automation (CCBBA) formally adopted Codabar for marking blood bags. It is common for bar codes to be concatenated for use in the blood bank industry. When two adjacent symbols use a D stop character, and the second symbol begins with a D start character, both can be scanned simultaneously, producing a concatenated bar code. Codabar consists of sixteen characters, zero through nine and the characters $, :, /,., +, and -. Codabar characters are made up of four bars and three intervening spaces consisting of a quiet zone, start/stop character, data characters, start/stop character and an ending quiet zone. The code has variable intercharacter spacing and code density of up to ten characters per inch. Depending on the specific character, eighteen different values can be assigned to bar widths and spaces. A check digit is not required; however, if additional data security is needed, a recommended modulus 16 check digit calculation is available. Twelve main characters (0 through 9, -, $) have one wide bar and one wide space. Special characters (: /. +) have three wide bars and no wide spaces. Four different start/stop characters (A, B, C, D) are encoded with one wide bar and two wide spaces. Last update 6/30/2004 Page 9 of 16

10 MSI/Plessey MSI/Plessey is commonly used in supermarket shelf labeling and formerly used in early library applications for scanning with various input devices to facilitate inventory reordering. Developed in England with formal specifications first dated in 1971, Plessey has several variants, MSI, Telxon and Anker Codes. MSI/Plessey code is sometimes referred to as pulse width modulated, wherein each pair of bars and spaces contain one bit of information. However, pulse width modulated codes do not carry significant technical benefits over more up-to-date symbologies. MSI/Plessey is a variable length, numeric, continuous bar code, and is not self-checking. A complete MSI/Plessey code consists of a start code, data characters, modulus 11 check digit, modulus 10 check digit (optional) and a reverse start character. Each character consists of four bars and four spaces. The zero bit consists of a narrow bar followed by a wide space; a one bit consists of a wide bar followed by a narrow space. Code 93 Introduced in 1982, Code 93 is similar to Code 39 except that it encodes more characters per inch. It was designed as a competitive symbology to Code 128 and to provide an extended character set to Code 39. Code 93 can be integrated into a system using Code 39 without changing system software but, only when a decoded, autodiscriminating input device is used. Code 93 is an alphanumeric, variable length, continuous bar code, and is not selfchecking. As of this publication, no national or international industry organization has officially adopted Code 93. The data characters of both Code 93 and Code 39 symbologies are the same; the start/stop codes and the check digits are not transmitted by the input device. Code 93, similar to Code 39, permits concatenation of consecutive bar codes containing a leading space character. The scanned leading space character is appended to a storage buffer. This process continues for all successive bar codes with a leading space and is added to previously stored ones. When a Code 93 bar code is scanned and does not contain a leading space, the entire buffer is transmitted and cleared. Last update 6/30/2004 Page 10 of 16

11 A complete Code 93 bar code consists of a leading guard bar (quiet zone), start code, data characters, C check digit, K check digit, stop code, termination bar and end guard bar (quiet zone). Code 93 characters consist of three bars and three spaces, except the start/stop character, which is represented by the symbol. Circle codes ($, %, / and +) are used as a preceding character of a two character sequence, and represent all 128 ASCII characters. Preceding characters are used to expand Code 93, similar to an extended ASCII character set for Code 39. Overall length of a character is nine modules, black or white and can be one, two, three, or four modules wide. Each character begins with a bar and ends with a space. The Code 93 character assignments shown in the following table represent only forty-eight of the total fifty-six characters-forty-three are the same as the Code 39 character set, and four are control characters. Every Code 93 bar code contains two check digits, C and K, which are variations of modulus 47 check digit. These check digits are not transmitted by input devices or printed in human-readable terms. Code 11 Developed in 1977 for labeling telecommunications components and equipment, Code 11 is a high density, numeric, variable length, discrete bar code and is not selfchecking. A complete Code 11 bar code consists of a start code, data characters, a C check digit, and occasionally a K check digit. Ordinarily when data characters consist of ten digits or less, only the C check digit is used. Last update 6/30/2004 Page 11 of 16

12 Three bars represent each data character with two intervening spaces for a total of five elements. Three different bar widths and two different space widths can represent each character: two wide, three narrow or one wide, four narrow. The character set consists of ten digits and a dash symbol (special character). Bar Code Terms and Abbreviations Alphanumeric is any character set containing letters, numbers and sometimes other characters such as punctuation marks. American National Standards Institute (ANSI) is a nongovernmental group responsible for the development of common bar code standards relating to government and industry. Code 39, Codabar and Interleaved 2 of 5 are the prefer#51619c symbologies. American Standard Code for Information Interchange (ASCII) is a 128- character code that enables information interchange between data processing, communication systems and compatible equipment. Aperture is the opening in an optical system that establishes the field of view. Aspect Ratio is the ratio of height to width in a bar code. A bar code twice as high as it is wide has an aspect ratio of 2; a bar code twice as wide as it is high has an aspect ratio of 0.5. Asynchronous is a digital communication in which there is no timing requirement for transmission. The transmitting device individually signals the start of each character. Autodiscrimination is a feature in bar coding equipment that defines and decodes various symbologies automatically. Autodistinguishing is a feature in bar coding scanners that recognizes and processes selected symbologies automatically. Automatic Identification Manufacturers (AIM) is an industry group active in promoting bar code standards. Automotive Industry Action Group (AIAG) is composed of representatives from major automotive industries responsible for the development of a common automotive standard relating to bar code symbology and format. Code 39 is the prefer#51619c symbology. Last update 6/30/2004 Page 12 of 16

13 Bar is the dark element comprising a bar code; a space is the area between the bars. Bar Code is a series of corresponding bars and spaces arranged to represent encoded data and used for automatic identification purposes. Bar Code Density is the number of characters that can be represented in a linear unit of measure often expressed in characters per inch, (CPI). Bar-Width Ratio is the ratio between the widest bar or space and the narrowest. Baud rate is the rate or speed at which data is transmitted. Bi-directional is the ability to successfully read data whether the scanning motion is from right to left or from left to right. CCD is an input device that photographs the bar code converting the optical image into an electrical image. (CCD stands for "charged coupled device".) Character Delay is the amount of delay inserted between each transmitted character. Check Character/Checksum/Check Digit is a character included within a bar code with the value mathematically based on the other characters within the bar code. It is used to check the accuracy of a read. Concatenation is the ability to link codes of the same type from multiple bar codes together in a series. Continuous Code is a bar code symbology where spaces between two characters are part of the code. Decoder is the electronic device that receives the signals from the input device, interprets them into significant data, and provides the interface to other devices. Delimiter is a character that marks the beginning or end of a unit of data. Density is the number of characters represented in a bar code usually expressed in characters per inch (CPI). Depth of Field is the distance between the maximum and minimum plane in which the code can be read. Discrete Code is a bar code symbology where spaces between two characters are not part of the code. Element is a term referring to either a bar or a space. European Article Numbering System (EAN) is the international standard bar code. Last update 6/30/2004 Page 13 of 16

14 Electrically erasable programmable read-only memory (EPROM) is another variety of ROM that allows the user to define the application program, prompts, edits, etc. Field is a group of characters defined as a unit. First Read Rate (FRR) is the percentage a bar code is successfully read on the first attempt. Fixed Beam Bar Code Reader or Scanner is an input device that uses a stationary beam to read bar codes. Fixed Length is a bar code in which the data elements must be a specific length. Guard Bars are bars located at the beginning, center and end of a bar code providing reference points for scanning. Health Industry Business Communications Council (HIBCC) is a group responsible for the issuance and control of bar codes within the health industry. Human-Readable is bar code data that can be read by a human whether it is numeric, alphabetic and/or special symbols that represent it. Infra#51619c is a beam of light used to scan a bar code that is invisible to the human eye. Infra#51619c is commonly used to prevent visual reading of the bar code by wands and non-contact scanners. Intercharacter Gap or Space is the space between two adjacent bar code characters in a discrete bar code, and does not contain any encoded information. Item Code is a five, or in some cases, a three-digit number that manufacturers assign to each product. International Article Numbering (IAN) See EAN. International Standards Organization (ISO) is developed a model (open systems interconnections) to describe data communications. Laser Scanner is an optical bar code reading device using a low-energy laser light beam as its source of illumination. Light Emitting Diode (LED) is a semiconductor often used as a light source in scanners. Magnetic Stripe Reader is an input device that reads and analyzes by detecting the absence or presence of a magnetic field. Manufacturer's Identification Number is the four or five digit number assigned to a manufacturer by the Uniform Code Council. See Item Code. Last update 6/30/2004 Page 14 of 16

15 Misread is an error that occurs when the data output of a reader does not agree with the data encoded in the bar code. Moving Beam Scanner is a scanner using a beam that oscillates to register the label rapidly and repeatedly. Non-Read is a scan attempt that does not yield any data. Number System Character is the first digit in a UPC bar code that identifies various numbering systems. Numeric is a character set that consists of only numbers. Omnidirectional is the ability to read any bar code from any angle. Parity is the state of being odd or even used as the basis of detecting errors in binary-coded data such as a bar code. Preamble is a character set transmitted at the beginning of each type of input data. Postamble is a character set that is transmitted at the end of each type of input data. Projection scanner is a moving beam, non-contact input device that simplifies reading bar codes on curved or irregular surfaces and designed to mount on top of a counter. Quiet Zone is a clear space that leads the start character of a bar code and follows the stop character. Reader Setup Menu is a bar code menu developed by the manufacturer to change functional options within an input device. Resolution is the narrowest element dimension that can be sensed by a particular reading device or printed with a particular device or method. Scanner is an electronic device producing infra#51619c or visible light and records the width and patterns of the bars and spaces simultaneously transmitting the data to a decoder. Self-Checking Code is a symbology whose symbols are designed to prevent a single printing defect by not allowing similar characters to be substituted for each other. Slot reader is a device designed to scan bar codes on identification cards, employee badges, tickets or forms with a high degree of accuracy and convenience. Space is the light element of a bar code, usually formed by the background. Last update 6/30/2004 Page 15 of 16

16 Start and Stop Characters is bar code characters that provide the scanner with start and stop instructions and scanning direction. Usually the start character is located at the left end of a horizontal bar code; the stop character is located at the right end. Substrate is the surface on which a bar code is printed. Symbol is a series of bar code characters, including start/stop characters, quiet zones, data characters, and check characters needed to form a complete, scannable entity. Symbology is a system for representing data in the bars and spaces of a bar code. Synchronous is a common timing signal established that dictates when individual bits can be transmitted, and, in which characters are not individually delimited and allows for very high rates of data transfer. Uniform Code Council (UCC) is a group responsible for overseeing and administering the Universal Product Code in the retail consumer industry. Universal Product Code-UPC is the standard bar code symbology for the retail grocery industry. Uniform Symbol Specification (USS) is the current series of symbology specifications published by AIM. Visible #51619c is a beam of light visible to the human eye that is used in wands and non-contact scanners to scan a bar code. Wand is a hand-held scanning device with a tightly focused light beam projecting from the end which detects the amount of light reflected back, enabling it to distinguish between light and dark objects that the tip touches. X Dimension is the width nominal dimension of the narrow bars and spaces in a bar code. Last update 6/30/2004 Page 16 of 16