The authors propose to use a set of independent observers to detect faults in communication systems that are modeled by finite-state machines. An algorithm for constructing these observers and a fast real-time fault detection mechanism used by each observer are given. Since these observers run in parallel and independently, one immediate benefit is that of graceful degradation; one failed observer will not cause collapse of the fault management system. In addition, each observer has a simpler structure than the original system and can be operated at higher speed. >