Barcode Xpress for Linux
PostNet
Specific to the US Postal Service is the PostNet (Postal Numeric Encoding Technique) examples can be found on of mail in the United States. Unique in that it varies the height instead of the width of the bars. Except for the start and end bars they are in groups of five with two long, three short. A PostNet can encode five, nine, or eleven digits, nothing else. It includes a checksum.
An example:
