We discuss the ability of a network with non linear relays and chaotic dynamics to transmit signals, on the basis of a linear response theory developed by Ruelle \cite{Ruelle} for dissipative systems. We show in particular how the dynamics interfere with the graph topology to produce an effective transmission network, whose topology depends on the signal, and cannot be directly read on the ``wired'' network. This leads one to reconsider notions such as ``hubs''. Then, we show examples where, with a suitable choice of the carrier frequency (resonance), one can transmit a signal from a node to another one by amplitude modulation, \textit{in spite of chaos}. Also, we give an example where a signal, transmitted to any node via different paths, can only be recovered by a couple of \textit{specific} nodes. This opens the possibility for encoding data in a way such that the recovery of the signal requires the knowledge of the carrier frequency \textit{and} can be performed only at some specific node.