Code 39 Extended was developed to provide a means of encoding additional characters that are not part of the Code 39 character set (for example, lowercase characters and additional symbols), and is essentially a superset of Code 39. Extended characters are encoded by using a pair of normal Code 39 characters. For example, a lowercase "a" is encoded by the character pair "+A". Code 39 Extended supports the full ASCII character set.
The ratio of wide to narrow bar width can be in the range of 1.8 to 3.4. The Barcode Xpress Code 39 uses a 2:1 wide:narrow bar width ratio.
An example: