The rapid development of the intelligent systems, which process data received from various types of sensors, raises the question for the change in the nature of the information they provide. In the proposed material is attempted to analyze the nature of the change of the a posteriori information for the presence of a certain type of events, processes, phenomena or objects received by sensors in the process of monitoring and analysis of the environment in which they operate. Because of natural and man-made interferences in the environment, in which operate the intelligent systems and the sensors, the decisions of the sensors are of a random nature. It is accepted, that the decisions of the intelligent systems are based on the criterion of minimum average risk or on derived from its criteria for a maximum ratio between the a posteriori probabilities for the presence or absence of the corresponding object, phenomenon or event. As an absolute maximum of this ratio can be achieved after an infinite number of decision-taking cycles by the sensors, the introduction of a threshold value for this ratio is proposed in this study. In the paper are examined one of the most common types of sensors - those working in discreet mode of operation. A mathematical description of the change of the a posteriori probability for the existence of a certain type of events, processes, phenomena or objects is proposed, and the dependence of this probability on the main characteristics of the sensors is analyzed. [ABSTRACT FROM AUTHOR]