Translations:Adventist Youth Honors Answer Book/Outdoor Industries/Dairying/27/en

Milking machines work in a way that is different from hand milking or calf suckling. Continuous vacuum is applied inside the soft liner to withdraw milk from the teat by creating a pressure difference across the teat canal (or opening at the end of the teat). Vacuum also helps keep the machine attached to the cow. The vacuum applied to the teat causes congestion of teat tissues (accumulation of blood and other fluids). Atmospheric air is admitted into the pulsation chamber about once per second (the pulsation rate), to allow the liner to collapse around the end of teat and relieve congestion in the teat tissue. The ratio of the time that the liner is open (milking) and closed (massaging or resting) is called the pulsation ratio.