An experimental reentry was generated in a two-dimensional array of electronic cells to study the influence of the distance on the interaction between that reentry and an external and autonomous pacemaker. For long distances $(d>~2/3\lambda$, where $\lambda$ is the reentry wavelength), the pacemaker is only able to modify the rhythm of the medium for periods faster than the reentry period. For shorter distances $(d<\mathrm{}2/3\mathrm{}\lambda )$, the pacemaker is able to modify the rhythm of the medium even for periods slower than the reentry period, giving rise to complex sequences of multiperiod output waves when both pacemakers are close enough.

• Received 10 March 1997

DOI:https://doi.org/10.1103/PhysRevE.57.949