We present a simple discretemodel for a minimal circuit in the hippocampal area CA3, which consists of various types of connected cells that differ in morphology and functional properties (pyramidal, basket and O-LM cells). This model allows for reproducing not only basic characteristics of the cells oscillations for all these types (period, amplitude and phase shift) but also to demonstrably explain the key property of switching between different rhythms using only one control parameter. The model results are confirmed via comparison with in vitro experimental results and discussed.