1.2.3. Barcode Format

Table 1.1. Plessey Barcode Format

start characterAny number of labels/characters/digitsChecksum / check digit / codeA stop / termination character / block / pitch barthe reverse start code
4it =1101XXX...(eg, 012345...)8bit(eg. 0110 0111)1bit=X(eg, 1)4bit=0011

In which:

  • the forward start code

    The forward start code is "1101". It defines the beginning of the encoded text.

  • the label / data digits

    The characters of the text to encode are hexadecimal values encoded as reversed BCD.

    Table 1.2. Plessey Bits Encoding Rule


  • the check code, for error detection

    The check code for error detection and correction is as CRC, using polynomial division.

    Is uses 2 characters, or 8 bits.

    The generator polynomial is g(x) = x8 + x7 + x6 + x5 + x3 + 1 with n=8, in binary "111101001".

  • the termination bar

    The termination bar follows the CRC. It's a full pitch bar.

  • the reverse start code

    The reverse start code, with the forward start code, are used to detect the direction of reading : from left to right or right to left.

    It's encoded as a reversed "0011".

    Reversed because the "0" is represented by a wide space and simple bar, and "1" as a simple space and wide bar.