MSI/Plessey
MSI, also know as Modified Plessey Code, is a relatively weak code which is inefficient in its use of space.
This code must begin with a start character and must end with a stop character. The start character is § (Chr$(167)) and the stop character is ¬ (Chr$(172)).
For convenience in typing the open bracket ( may be used as the start character, and the close bracket ) may be used as the stop character.
Normally this code has a single Modulo 10 check digit, somewhat peculiar algorithm used for this is include in the dFont program. However, there are two variations of a double check digit form in common use. One uses a (standard) Modulo 11 check digit before the Modulo 10 check digit, the other uses two Modulo 10 check digits.
If Extra1 is set then a Modulo 10 check digit is calculated and inserted before the normal checkdigit.
If Extra2 is set then a Modulo 11 check digit is calculated and inserted before the normal checkdigit.
Some scanning equipment cannot read both forms. (in fact some scanning equipment cannot read either of the two check digit forms). Check your scanners documentation to ensure that you choose an appropriate combination.
The dFont program provided with the dLSoft Barcode fonts calculates the single Modulo 10 check digit for MSI codes, and the source code is provided and may be adapted to the users needs - for example, for automating the calculation in a spreadsheet or database.
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