Pitney Bowes FastPac DI900 Manuallines page 58

3 • Barcode Theory
Barcode
3 of 9
Symbology
✍
TIP: If customers do
not use the human
readable barcode
fonts, it is important
to print the code data
somewhere on the
page for debugging
purposes.
✍
TIP: Byte "0" and "6"
are referred to as
the "stop and "start"
bytes and are ef-
fectively ignored by
the system for scan
functionality.
3-6
Understanding the Requirements at the Bit Level on the Barcode
The first thing to do is understand the construction of a barcode. The code be-
low gives a simple example of a 3 of 9 barcode.
*20001*
3 of 9 Barcode
(human readable)
This code is made up of the following components.
Byte 0 1
number
* 2
Barcode
Symbol * 2
Binary ignored 00010
Each character in table above is equal to 1 Byte of information. The code is
broken into several bytes so any information you wish to store can be stored
(encoded) into 1 or if necessary more of these bytes.
The *'S at the start and end of the code (Bytes 0 and 6 in the example above)
are just start and end markers and are required for the 3 of 9 code. These
can be thought of as having the same function as the Benchmark and Safety
marks in an OMR code. Unlike the Benchmark and Safety marks in an OMR
code, the *'s are not User Definable and cannot be removed, therefore they
will be omitted from the remainder of this discussion.
The decoded binary information in Table 1 above shows that the code is just
made up of a simple binary code that represents each number. Each Byte
is broken up into 5 bits, not the conventional 8 bits. The table in Appendix B
– Code 3 of 9 Character Set and PlacementshowsAppendix B – Code 3 of 9
Character Set and PlacementAppendix B – Code 3 of 9 Character Set and
Placement shows how a byte represented as a character can be converted to
5 bits.
Each bit of the barcode can be thought of as having the same purpose as a
mark in an OMR code. A bit set to 1 is like having an OMR mark printed on
a page, and that Bit Set to 0 is like having the same Mark not printed on the
page.
2001
2 3 4
0 0 0
0 0 0
00000 00000 00000
3 of 9 Barcode
(non-human readable)
5 6
1 *
1 *
00001 ignored
SV61314 Rev. A