POSTNET (Postal Numeric Encoding Technique) was designed by U.S Post Office for encoding zip code information.
Character set of POSTNET barcode symbology consists of numbers (0-9) containing a length of 12-14 digits.
Structure of POSTNET
Structure of POSTNET has start/stop character in form of full bars, numbers (0 to 9) of variable length. Each character is represented using five bars – three are small and left two includes long bars and check digit (calculated according to modulo 10).
Mainly used for tracking zip code information and improving speed & delivery of mails in U.S Postal Office.