Abstract: A cereal milling machine having a stock reservoir for incoming stock to be milled, a pair of motor driven feed rolls for metering the stock at a controlled rate from the reservoir, and a pair of grinding rolls for receiving the stock from the feed rolls. A stock level control system comprises a vertical array of spaced capacitive switches located outside the reservoir, each sensor producing an electrical signal according to the presence or absence of stock at the level of the individual sensor, a variable speed motor driving the feed rolls and a micro-computer connected to the sensors and to the motor via an inverter to accelerate or decelerate the motor as a result of changes in the level of stock in the reservoir. The control system ensures a substantially constant mean level of stock in the reservoir and protects the grinding rolls.