On the example of three coupled identical ring oscillators, the coexistence of two stable homogeneous tori embedded in each other, corresponding to the regimes of successive activity of oscillators, is established. It is shown that a small stable torus is born from a stable periodic regime as a result of supercritical Neirmark-Sacker bifurcation. A large torus is formed as a result of saddle-node bifurcation. We present a study of the formation of tori coexistence as well as long transient dynamics on the threshold of bistability.