MagTek TTL - Manual (Page 17)

13
SECTION 3. LRC CALCULATION
The formula for calculating LRC below uses Track 2 as an example. Perform the following:
1.
Write the value for each character (see examples below and Appendix A).
2.
Do not use the odd parity bit (P) in the formula for calculating LRC calculation.
3.
Count the number of one bits in each of the 4 vertical columns.
4.
Enter a zero or one in the LRC position so that each vertical column has a even number
of ones (not the parity column {P}).
5.
After all 4 vertical columns have their LRC bit affixed, affix odd parity to the LRC
character itself.
Examples:
P 8 4 2 1 P 8 4 2 1 P 8 4 2 1
B 0 1 0 1 1 B 0 1 0 1 1 B 0 1 0 1 1
0 1 0 0 0 0 0 1 0 0 0 0 0 1 0 0 0 0
F 1 1 1 1 1 1 0 0 0 0 1 1 0 0 0 0 1
_______ F 1 1 1 1 1 2 0 0 0 1 0
4 0 0 1 0 0 _______ 3 1 0 0 1 1
Where: 5 1 0 1 0 1 F 1 1 1 1 1
"B" is the start sentinel _______
"F" is the end sentinel 4 0 0 1 0 0
The LRC is under the line