 Each field is scanned in 1/60 second under the 525-line system (or 480i – often incorrectly referred to as NTSC) or 1/50 of a second under the 625-line system (or 576i – often incorrectly referred to as the PAL).With interlaced systems there are an odd number of lines in each frame.This means that there is a half line offset between the fields, therefore the lines in the second field will be positionally interleaved with the lines in the first field.