The class of multi-loop automatic control systems is considered in which several control inputs are produced for maintaining the main controlled quantity. It is shown that the methods developed for well-known multi-loop structures with several controlled variables can be used in analyzing and synthesizing such systems. It is demonstrated that, if multi-loop automatic control systems producing several control inputs and comprising local automatic control systems with several controlled variables contain inertial loops separated by a low-inertia leading loop, then such loops can be decoupled by frequency. A multi-loop system for automatically controlling steam temperature in a once-through boiler is studied. Peculiarities connected with implementation of such structures are described taking into account the design features of boiler equipment and current requirements for setting up technological modes of operation.