What Does Postal Numeric Encoding Technique (POSTNET) Mean?
The Postal Numeric Encoding Technique (POSTNET) is a bar code method used by the United States Postal Service to assist in properly routing mail. In POSTNET, the ZIP code is formatted as a bar code, with each digit represented by five bars. The POSTNET codes always start and end with full bars.
Techopedia Explains Postal Numeric Encoding Technique (POSTNET)
The Postal Numeric Encoding Technique encodes the ZIP code and destination address in a bar code format on postal mail. Techniques like error detection and correction are used in this system. Each digit consists of a set for five bars, two of which are full bars and three are half bars. Full bars represent "on" bits while half bars represent the "off" bits on the pseudo-binary code. Bar codes come in 5-digit (32-bar), 6-digit (37-bar), 9-digit (52-bar) or 11-digit (62-bar) formats.
POSTNET is largely being replaced by Intelligent Mail bar code which began implementation in 2013.