单项选择题
A.AM1 B.RZ C.NRZ
A...1 0 0 0 0 0 0 0 0 1 1 1 0...... B.+1 -1 0 0 -1 +1 0 0 +1 -1 +1 -1 0...... C.+1 0 0 0 0 0 0 0 0-1 +1 -1......
A.HDB3 B.AM1 C.RZ