Apparatus and methods for controlling a system that operates responsive to a plurality of input control signals are disclosed. During operation the system generates a plurality of output status/control signals. A master controller has at least first and second controllers. The first controller outputs and inputs signals over a first communication path, and the second controller outputs and inputs signals over a second communication path. The first and second controllers output signals based on input signals received over the first and second communication paths, respectively, and also based on stored control data. A plurality of input/output modules are provided. Each of the input/output modules has first and second slave controllers. The first slave controller of each of the input/output modules inputs and outputs signals over the first communication path to the first controller, and the second slave controller outputs and inputs signals over the second communication path. Each of the first slave controllers outputs and inputs signals to and from a first input/output circuit, and each of the second slave controllers outputs and inputs signals to and from a second input/output circuit. Each of the input/output modules also includes a combiner circuit. At least some of the input control signals for controlling the system are generated by the combiner circuit of each input/output module based on signals output from both the first and second input/output circuits. The output control signals for controlling the system are generated based on output status/control signals from the system that are coupled to each of the first and second input/output circuits of the input/output modules.