ABSTRACT. This work deals with the observability analysis for LHS’s considering both known and unknown inputs and constrained discrete dynamics, modeled by Petri nets. For this, the concept of eventual observability is recalled as the possibility of uniquely determining both the discrete and the continuous states after a finite number of switchings. In this way, the information provided by the continuous and the discrete outputs of the LHS can be combined to determine the discrete state after a finite number of switchings. Next, based on the knowledge of the visited locations, a continuous observer can estimate the continuous state. It is shown that under this approach the observability conditions are greatly relaxed with respect to other approaches in the literature, in particular, neither the observability of the linear systems nor the observability of the underlying discrete event system are required.