In the skip field format, video is recorded by only one of the two video heads, resulting in only one field being recorded. On playback, the second rotating head sweeps the same track as the first, effectively repeating the same field. Since the tape has advanced by the time the second head was coming into position for the second sweep, the "B" head was placed slightly behind and below the "A" head as opposed to 180 degrees apart and on the same horizontal plane as in other schemes. The positioning of the "B" head was critical and set by the factory and thus no provision for field adjustment is possible.