When in the course of perhaps hundreds of thousands of revolutions one hole in each wheel reaches the same point at the same time, when thirty holes are lined up, in other words, the beam of light goes straight through the machine, strikes a sensitive photo-electric plate and stops the machine instantly.
Kapag sa kurso ng marahil daan-daang libo ng revolutions isa butas sa bawat gulong na umabot sa parehong point sa parehong panahon, kapag tatlumpung butas ay may linya up, sa ibang salita, ang mga poste ng ilaw goes tuwid sa pamamagitan ng makina, strikes isang sensitibong litrato -electric plate at huminto ang makina agad.