Fig. 6.

Continuation in the parameter a, for $b=-0.5$ and $\mathit{\gamma }=1$, $\mathit{\omega }=2$, $\mathit{\alpha }=\mathit{\beta }=1$. The branches show that, with suitable combination of the parameters, it is possible to have stable in-phase, anti-phase and phase-locked oscillations by varying a. Solid lines represent stable and dashed lines unstable states of (11)