PDF 417

PDF 417 is perhaps the best known multi-row stacked linear symbology.  It has been in the field for a long time and is used in many applications, such as drivers licenses, airline boarding passes and shipping labels.

The design of PDF417 provides for the symbol being “line sannable”.  First of all, each row is composed of self-clocking characters, much the same way as an ordinary linear bar code.  The structure of each character is 8 elements (4 bars and 4 spaces) arranged within 17 unit modules.  Hence the ‘417′ in the name of the symbology.  (The ‘PDF’ part stands for ‘portable data file’ and suggests that the data capabity of the symbol is large enough to represent all of the data associated with the item that the label is on, as opposed to a number that refers to a record in a non-portable data file (such as a price look table) in a computer data base.

Each row can be read in a way that is similar to the process of reading a linear bar code.  However, each row further contains a special character at each end (adjacent to the start and stop characters) which identify the row number within the symbol for this row.   There is also other information in these special characters, including the total number of rows and the total number of columns in the symbol.  In this way, a scan of a PDF 417 symbol can yield part of the decode information of the sybmol which can be combined with other scans (of the other rows) to result in a complete decode.  Thus PDF 417, like other multi-row stacked symbologies are “line scannable”.  It is not necessary to get a picture of the whole symbol in a two dimensional image to read a PDF 417 symbol, as it is for matrix symbologies.  This distinction has been at the heart of much controversy and dispute over which symbology was “better”: PDF 417 or Data Matrix.  In truth, neither is “better”, but each symbology used different trade offs between ease of reading, resilience to damage, and space efficiency within the printed symbol.

Product	Reason to use this product for verification of PDF417	Example Product Picture
TruCheck Laser USB	For Windows PC based verification of linear and stacked symbologies.
TruCheck 201	For stand alone verification of linear and stacked symbologies.
TruCheck 2D USB	For imager based verification of 2D Matrix Symbologies and small linear and/or stacked symbols, especially DataBar which is especially small.
TruCheck Inline	For high speed online verification of PDF417 and 2D Matrix Symbologies.