In this paper, we introduce the notion of transfer function for linear hybrid systems in the presence of time-driven periodic jumps. Such concept is employed to extend frequency-domain analysis tools - well-known and extensively used in the context of purely continuous or discrete time systems - to a class of hybrid systems. In particular, knowledge of the transfer function permits firstly the computation in closed-form of the complete forced (state or output) response of the hybrid plant. Moreover, the hybrid transfer function allows for the frequency-domain definition of the notion of 0-th moment of the underlying system, which is instrumental, e.g. for the solution to model reduction or system identification problems. It is shown, in add...