This work concerns the response of systems to external forcing. We study models composed by units coupled through both attractive and repulsive links, and observe that the transmission of an external weak signal is optimal for a given fraction of repulsive links. Competitive interactions are taken as a source of disorder, as an alternative to previous studies where response was amplified by disorder induced by noise [1] or diversity [2]. Resorting to numerical simulations and analytical calculations, we propose a ‘macroscopic mechanism of resonance’, considering the effect of disorder on the stationary state distribution, in the absence of signal. Our emphasis here is on several prototypical systems, like Ising networks or the phi-4 model. Our choice of bistable units is related to the role bistability plays in Stochastic [1] or Diversity induced resonance [2] studies. We show that in the composite system the maintenance of bistability is not required, and in fact the optimal disorder is the one that destroys the system bistability. [3] References 1. L. Gammaitoni et al, Stochastic resonance, Rev. Mod. Phys. 70, p. 223 (1998). 2. C. Tessone, C.R. Mirasso, R. Toral, J.D. Gunton, Diversity induced resonance, Phys. Rev. Lett. 97, 194101, (2006). 3. T. Vaz Martins and R, Toral, Resonance induced by repulsive links, in V. In, P. Longhini, A. Palacios (Eds), Applications of Nonlinear Dynamics: Model and Design of Complex Systems, Springer Verlag, p. 439-445, (2009)