1) When an external trigger signal is input during the period of field 1 scanning, the field A is equivalent to field 1, and the field B to field 2. The CCD reads
out the field 1, then field 2 to output the video signals A and B. When an external trigger signal is input during the period of field 2 scanning, the field A is
equivalent to field 2, and the field B to field 1. The CCD reads out the field 2 first, then the field 1 to output the video signals A and B.