We have investigated numerically the behaviours of identical FitzHugh-Nagumo systems, which are coupled into topologies of regular one-dimensional lattice, small-world network and scale-free network, and driven by white noise and an extal signal. We found that when a number of uniform systems are coupled into a network, the system’s signal-to-noise ratio remains at a high level in a wider frequency range than in the case of a single oscillator. Different architectures manifest different impact, with the scale-free network being the most remarkable. Results presented here suggest a possible approach to improve the sensitivity of a system to extal signals and are helpful for designing communication equipments.