Labels:text | screenshot | rectangle | font | line | number | diagram OCR: BIPOLAR SIGNALING + 0 1 0 1 1 0 1 0 + 0 1 0 1 1 0 1 0 0 A. Bipolar nonreturn to zero B. Bipolar return to zero Figure 2. Bipolar signaling indicates a mark or I with alternating positive and negative values -- alternate mark inversion (AMI) and spaces or Os are indicated by zero values. Two successive marks with the same polarity constitute a bipolar violation, or BPV.