Subsequent number

                  SS7-ISUP

           8  7  6  5  4  3  2  1
        1  b  a  a  a  a  a  a  a
        2  gg-2nd-ggg  gg-1st-ggg
        .
        .
        n  --filler--  gg-nth-ggg

a) spare

b) Odd/even indicator
g) Address signal
Filler