Hand Held Products Quick Check Bar Code Verifiers 800 User Manual

Contents

6 - 4 Quick Check® 600/800 Series User’s GuideSymbology CharacteristicsYour Quick Check 600/800 Verifier can handle bar code symbologies with avariety of characteristics. To help understand symbologies, you should befamiliar with the following commonly used terms:• Code refers to the actual data contained in the bar code symbol, such as apart number, serial number, transaction code or other type of data.• Symbol refers to the actual arrangement of parallel bars and spaces thatencode the data.• The character set describes the range of data characters that can beencoded in a given symbol. For example, UPC uses onlynumbers and is called a numeric symbology, whereas Code 39 usesalphabetical characters, numbers and special characters.• There are two symbology types, discrete and continuous.• In a discrete code, each character stands alone and can be decoded.Between characters is a loosely toleranced intercharacter gap whichcontains no information. Every discrete character has a bar on eachend. One example of a discrete code is Code 39.• In a continuous code, there are no intercharacter gaps. Everycharacter begins with a bar and ends with a space. The end of onecharacter is indicated by the start of the nextcharacter. An example of a continuous code is UPC.• The bar and space widths can vary within or between symbologies;those with only two-element widths (wide and narrow) versus thosethat use multiple widths.• Two-width symbologies, such as Code 39, have a ratio of wide tonarrow typically between two and three.• Multiple-width symbologies, such as UPC, allow the bars andspaces to assume more than two different widths. Most multiple-widthsymbologies have characters whose length is subdivided into apredetermined number of modules. In addition, the width of each baror space is always an integral number of modules.Bar code symbologies vary on the amount of information that can be encoded ina given length. Usually, only characters have a specified density, since theoverall length of a symbol must include other characters. These other charactersmay include a start/stop code and a check character.• A start code is a pattern of bars and spaces that appears at the beginning ofa symbol to inform the reading tool where the symbol begins.• A stop code is a pattern placed at the end of a symbol for marking the end ofthe data characters. Sometimes the start and/or the stop characters alsoindicate the scanning direction.Quiet zones are areas at the beginning and end of a bar code symbol that allowthe optical equipment to differentiate a bar code from other printed material.Most of the symbologies in use today are bidirectional; this means that they canbe read by a scanner either left-to-right or right-to-left without affecting thedecoded data.