A “control interlock” to stop air entering a dairy milking vacuum system. When milking cows, a pulsation unit lets atmospheric air into chambers at the milking claw which makes a gripping motion and then milk flows from the cow. When milk stops flowing, existing controls detach the claw from the cow but does not stop the pulsation air flowing. Because there is a period of time from detachment of one cow till the next cow starts being milked, the pulsation unit is working and allowing unneeded atmospheric air to enter the milking vacuum system. Less air means less energy used by the vacuum pump motor.