Recently control system safety against device faults, especially sensor faults, has attracted widespread attention. This paper is based on redundancy of truly important information for device fault tolerance, and introduces a new decision rule on the information. To put the assertion more concretely, this paper considers the state of a plant as the truly important information. To obtain redundancy of the information, it uses three redundant subsystems, where each subsystem consists of a sensor set and an observer. Only the estimated state adopted by an analogue and vector-valued decision rule is used for state feedback. In a sensor fault case the rule almost always adopts a correct state estimated by a normal observer just like majority decision, so that the total system has the sensor fault tolerance.