The Code 39 barcode should always be preceded and followed by a quiet zone that should be at least 10 narrow bars (NB) – (aka 10 times the NB). It encodes 43 different upper case alphabetic, numeric, graphic characters plus a space and has the capability to encode all 128 ASCII characters. The key drawback to using Code 39 is that it is a low density code that takes more space than compact codes such as Code 128 and thus may not be appropriate for small labels.Įvery Code 39 character consists of 5 bars and 4 spaces with 3 of them wide (for a binary value of 1) and 6 narrow (for a binary value of 0) for a total of nine elements. The limits are set solely by the size of the label. A variable length code has no limit to the number of characters that can be encoded.Self-checking means that a single printing defect will not cause a character to be transported to another valid character in the same symbology.Each character is separated from its neighbors by inter-character gaps that contain no information. In a discrete code, each character can stand-alone and be decoded independent of other characters.It is a discrete, self-checking, variable length code: No matter what you call it – Code 39, Code 3 of 9, USS Code 39, USD-3, Alpha39 or Type 39, this barcode has remained one of the most popular codes in use today – except for the UPC code used on all retail merchandise.Ĭode 39 was the first alphanumeric code to be developed back in 1974 and is still one of the most commonly used symbologies for electronics, healthcare, and government.