Barcode 39

Encryption uses an encoding table with 43 characters: the 26 capital letters, the 10 digits and some special characters (-, ., $, /, +, % and ' ' (space). The character * can appear but it does not exist, it is only used as a delimiter for start and end.

Each character has 5 black bars and 4 white bars (9 elements in total) starting with black and alternating white and black. Each band can have 2 widths: narrow or wide (generally 3 times larger), so it is possible to binarize the code (1 for thin bands, and 0 for wide bands). Also, in these 9 elements, always 3 bands are larger, hence the name of code 39.

A barcode 39 starts with * and ends with *. Here is the character map:

Each character has 5 black bars and 4 white bars (9 elements in total), it is therefore possible to binarize the (1, 11 or 111 for black bands according to its width, 0, 00 or 000 for white bands). In these 9 elements there are 3 which are larger (between 2 and 3 times as wide) and 6 thinner. The code starts with * and ends with *.

0	|||▮▮|▮||	1	▮||▮||||▮
2	||▮▮||||▮	3	▮|▮▮|||||
4	|||▮▮|||▮	5	▮||▮▮||||
6	||▮▮▮||||	7	|||▮||▮|▮
8	▮||▮||▮||	9	||▮▮||▮||
A	▮||||▮||▮	B	||▮||▮||▮
C	▮|▮||▮|||	D	||||▮▮||▮
E	▮|||▮▮|||	F	||▮|▮▮|||
G	|||||▮▮|▮	H	▮||||▮▮||
I	||▮||▮▮||	J	||||▮▮▮||
K	▮||||||▮▮	L	||▮||||▮▮
M	▮|▮||||▮|	N	||||▮||▮▮
O	▮|||▮||▮|	P	||▮|▮||▮|
Q	||||||▮▮▮	R	▮|||||▮▮|
S	||▮|||▮▮|	T	||||▮|▮▮|
U	▮▮||||||▮	V	|▮▮|||||▮
W	▮▮▮||||||	X	|▮||▮|||▮
Y	▮▮||▮||||	Z	|▮▮|▮||||
-	|▮||||▮|▮	.	▮▮||||▮||
	|▮▮|||▮||	$	|▮|▮|▮|||
/	|▮|▮|||▮|	+	|▮|||▮|▮|
%	|||▮|▮|▮|	*	|▮||▮|▮||

A wide band is 3 times thicker than a thin band.

Decryption requires to perform a reading of the bar according to EAN-128 standard.

Many app for smartphones or laser handshowers facilitate this work.

Associate with each character the value of its position in the alphabet of 43 characters 0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ-. $/+% * (starting from 0)

Add these values and calculate the result modulo 43. The control character is the one in position (sum%43) in the alphabet.

The barcode has a classic graphical form (black and white lines) or a binary equivalent (1 or B for black and 0 or W for white lines).

The barcode may have a variable length. It begins and ends with the character *.

The bar code consists of lines in groups of 9 which 3 are wider, hence the name 3 of 9 or 39.