Why have chaotic techniques not been applied well in informatics? Chuas circuit was invented two decades ago,though there has been several decades past since the invention of chaotic theorem? This paper proposes four crucial issues,which should be solved completely before solving the problem of chaotic applications.A chaotic circuit has been put forward in this paper,to establish the correspondence between external signals and chaotic orbits.The chaotic orbit space is transformed into an orderly space,therefore the four crucial issues are partly solved.