User's Manual

Bar Code SymbologiesAppendix —B
405700 Series Color Mobile Computer User’s Manual
When programming the computer for Code 39, it is important to set the
symbology limit as close as possible (minimum and maximum bar code
lengths being scanned). Doing so keeps the computer bar code processing
time to a minimum and conserves battery power.
Bar code readers can respond to Uniform Symbology Specification sym-
bols in non-standard ways for particular applications. These methods are
not for general applications, because of the extra programming required.
Code 39 Full ASCII is one example of non-standard code.
Note: See page 398 to scan several Code 39 bar code labels available to
change settings on y our 751G Computer.
Encoded Code 39 (Concatenation)
If the first data character of a symbol is a space, the reader may be pro-
grammed to append the information contained in the remainder of the
symbol to a storage buffer. This operation continues for all successive sym-
bols that contain a leading space, with messages being added to the end of
previously stored ones. When a message is read which does not contain a
leading space, the contents are appended to the buffer, the entire buffer is
transmitted, and the buffer is cleared.
Encoded Code 39 (Full ASCII)
If the bar code reader is programmed for the task, the entire ASCII charac-
ter set (128 characters) could be coded using two character sequences: a
symbol (“$”,“.”,“%”,“/”) followed by a letter of the alphabet.
Code 93
The introduction of Code 93 provided a higher density alphanumeric
symbology designed to supplement Code 39. The set of data characters in
Code 93 is identical with that offered with Code 39. Each character con-
sists of nine modules arranged into three bars and three spaces.
Code 93 uses 48 of the 56 possible combinations. One of these characters,
represented by a square, is reserved for a start or stop character, four are
used for control characters, and the remaining 43 data characters coincide
with the Code 39 character set. An additional single module termination
bar af ter the stop character concludes the final space.
Code 93 is a variable length, continuous code that is not self-checking. Bar
andspaceswidthsmaybeone,two,three,orfourmoduleswide.Itsstruc-
ture uses edge-to-similar-edge decoding. This makes the bar code immune
to uniform ink spread, which allows liberal bar width tolerances.
Code 93 uses two check characters. Its supporters believes this makes it the
highest density alphanumeric bar code. The dual check digit scheme pro-
vides for high data integrity. All substitution errors in a single character are
detected for any message length.