We have recently observed that a passive barrier separating two excitable chemical media may transform a train of incoming pulses. Such result may be obtained in numerical simulation which use a model FitzHugh - Nagumo type dynamics as well as in "realistic" calculations based on Rovinsky-Zhabotynski or Oregonator models of Belousov-Zhabotynski reaction. The numerical calculations demonstrate that at the barrier a periodic train of pulses may be transformed into a complex output signal. The ratio of frequencies of the output and the input signals, plotted as a function of the barrier's width or as a function of the input signal frequency has a devil's staircase like shape.