PAN Number's LAst Digit's Logic

Any Body Know's Last Digit (Check Digit's) Logic/Arithmetic , at what reasoning It is being applied by Deptt. of Income Tax . Is it an ELEVEN MODULO CHECK DIGIT or Something Else ??

First Three Characters (Range AAA to ZZZ) fourth Digit if (P-Personal, C-company, B-BOI , F- Firm etc.) Fifth Digit ( is always First Character of Lastname/Surname of Assessee) From Sixth to 9th always Numerals (0001 to 9999) .

The Tenth Last Digit (Check Digit) always Alphabet !! what is The reasoning / Logic / Arithmetic/basis of Calculation of that Check Digit ?? My Question is what is The Methodology being adapted by Department to allot this CHECK DIGIT ?? IF we know That we can apply the same in developing Softwares like E-TDS etc. to Avoid DATA Feeding Errrors.