This article deals with specification, refinement and verification approaches for systems designed with synchronized components. First of all, we define a synchronized composition of components. Transition systems are used to specify or/and to model synchronized component-based systems. Second, we give refinement semantics for these component-based systems before proposing a method to verify the refinement of a whole system from the weak refinement of its components. We also present SynCo (for Synchronized Component-based Systems): a tool we are implementing using our method. Third, a compositional way to verify safety properties is proposed: the unreachability of a (set of) state(s) can be efficiently ensured for a synchronized component-based system. The different aspects of our work are illustrated on an industrial example of a wind-screen wipers system composed of a control lever, a rain sensor and two (left and right) wind-screen wipers.