Oki 390/391 Handbook page 52

Code 128
Code 128 has 106 different characters, each of which can have any one of three differ-
ent meanings depending on which code set (A, B, or C) is engaged. A special code at
the beginning indicates which set is engaged: three shift codes are also available for
use within the bar code to indicate a change in the code set engaged, as required.
Interleaved2 of 5
Inerleaved2 of 5 bar coding is used mainly in the distribution industry. Two digits are
encoded: one in the bars and one in the spaces.
Postnet
Postnet bar coding is used by the U.S. Post Office for sorting mail by automated equip-
ment. It incorporates a coding system using five bars and four spaces for each digit.
ML390/391 Turbo Printer Handbook 45