The work presented in this article shows, through a case study, the different stages of designing a fault tolerant system; a system which can tolerate faults without losing its operational capability. This system includes a gripper mounted on the wrist of a robot manipulator. First the faults were identified, then the residual generation stage was designed. Analyzing this residual allows us to show that artificially injected faults can be detected and an alarm is generated for an emergency stop command. With regards to the gripper, we have only dealt with the faults we were able to solve thanks to the accommodation stage which must control both hardware and software reconfigurations. The considered faults originated in the electronic interfaces and for an efficient supervision we have designed the whole gripper control. The electronic interfaces concerned by fault occurrence are duplicated to ensure robot task continuity.