Appendix a - bar code symbologies – ID Innovations Bar code Slot Reader - Visible Red and Infra Red User Manual
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Appendices
25
Appendix A - Bar Code Symbologies
&RGH
Encodable Character Set
26 upper case letters (A-Z)
10 digits (0-9)
7 special characters (
SPACE
- . + $ / %)
Data Character Density
6.25 CPI
(based on X = 0.010 inch (0.25 mm), 3:1)
Non-Data Overhead
Equivalent to 2 symbol characters
Symbol Length
Variable
Check Digit
Optional (Modulo 43)
Special Features
Message Append
Code 39 Characteristics
Code 39 is a variable length alphanumeric code, supporting numbers, capital letters, and seven special characters. Each
character consists of nine elements, made up of five bars and four spaces. Three out of nine elements are wide, thus the 3 of 9
designation.
Code 39 is a discrete code, meaning there is a space (intercharacter gap) between each character. The size of the intercharacter
gap is generally the size of one narrow element. This code requires a unique start and stop character at the beginning and end of
the bar code. This character is the '*' character and may not appear in the data for the bar code.
It is sometimes advantageous to break up long messages into multiple, shorter symbols. If the first data character of a Code 39
symbol is a SPACE, the reader may be programmed to append the data following the space to a concatenation buffer. This
operation continues for all successive Code 39 symbols with a leading SPACE, with messages being added to the end of the
previously stored messages. When a Code 39 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.
Note: Scanning a bar code that begins with a - (dash) will clear the concatenation buffer and no data will be output. In addition
if you scan a bar code with a different symbology, the concatenation buffer will be cleared and the new bar code will be output.
For applications requiring enhanced data security, a Modulo 43 check digit can be used. When used, the check digit immediately
follows the last data character. The check digit is calculated as follows:
1. Each character in the data is assigned a numerical value from the following table:
Char Value Char Value Char Value Char Value
0
0
B
11
M
22
X
33
1
1
C
12
N
23
Y
34
2
2
D
13
O
24
Z
35
3
3
E
14
P
25
-
36
4
4
F
15
Q
26
.
37
5
5
G
16
R
27
SPACE
38
6
6
H
17
S
28
$
39
7
7
I
18
T
29
/
40
8
8
J
19
U
30
+
41
9
9
K
20
V
31
%
42
A
10
L
21
W
32
Char values for Modulo 43 check digit calculation
2. Sum all of the numerical values for each character in the bar code.
3. Divide the sum by 43.
4. The remainder is the value for the check digit. Use the table in step 1 to look up the corresponding character.
For example, to calculate the check digit when the Code 39 data = "CODE 39"
*
A
B
C
D
1
2
3
4
*
Code 39 - 13 Mil