Synchronization in networks has been an active research area in recent years. In this paper we consider networks where the only measurements available to an agent are relative output information from their neighbors. No direct information of its own internal agents is available nor is there an exchange of internal controller states with neighboring agents. We consider the homogeneous case where all agents are identical SISO linear systems of arbitrary order. The prime extension compared to earlier work is that we only assume the systems to be weakly-non-minimum-phase.