Introduction
MSI Data Corporation introduced MSI from the original Plessey Code.
Therefore, MSI is also known as Modified Plessey. It is mainly used in
retail business.
MSI/Plessey is a fixed-length, non-self-checking symbology.
Most applications still support MSI only for backward compatibility,
because MSI/Plessey is based on Pulse-Width Modulation technology.
MSI requires start/stop characters. MSI is used to encode numeric data
and check digit is required to add at the end of the data.
Variants
MSI is sometimes called Plessey Code or MSI/Plessey.
Structure of a MSI/Plessey barcode
A typical MSI/Plessey barcode has the following structure:
- A start character
- Message encoded
- check digit
- A stop character
Check Digit Calculation
MSI uses one or two check digits, which may be calculated in a number of
different ways. As such,
it is really up to the software application to implement and check the
check digit(s).
The most common methods of calculating MSI check digits are:
Modulo 10
To calculate the modulo 10 checksum digit, use the following steps:
- Create a new number using every other digit from the original code
such that the right-most digit of the new number is the right-most digit
of the old number. For example, in the barcode above the data we encoded
was "8052". In this case, the "new number" is 02.
- Take the new number calculated in step 1 and multiply it by 2. In
this case, 02 * 2 is 4.
- Add the digits of the value calculated in the previous step (4), and
add it to the digits that were not used in step 1 to form the new number.
In our example, this would be 4 + 8 + 5 = 17. The "4" comes from step 2,
the 8 and 5 come from the "8052" and are the digits that weren't used to
form the new number in step 1. If the result from step 2 were, for
example, 123, then we'd add 1 + 2 + 3 = 6 (plus the digits that weren't
used from step 1).
- Do a modulo 10 calculation on the result of step 3. In this case, 17
modulo 10 = 7.
- The check digit is the value which, added to the result in step 4,
equals 10. In this case, we must add 3 to 7 to get 10-so the check digit
is 3.
Web Tool
At barcode knowledge library we provide free web-based utilities for
readers to calculate check digits, performing number conversions. To
calculate check digits, refer to this page. If you have
purchased Morovia MSI/Plessey Font, you may consider checking out this
page for additional utilities for character mapping.
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