system using as reference the phase of the clock in the vertex A (= clock $O_{1}$). This reference is arbitrary: any of the clocks can be used as the reference clock with the same results at the end, since the system is symmetric. We compute the effects of all phase differences and perturbations when the clock at A makes a complete cycle returning to the initial position. Without loss of generality, we consider the next working hypotheses.

1.  \[work1\]The initial phase of clock at A at $t=0^{-}$ is zero, i.e., $\psi_{1}(0^{-})=0^{-}$, the minus ($-$) superscript means that at the instant $0^{-}$ clock $1$ is just about to receive the internal energy kick from its escape mechanism.

2.  \[work2\]We consider that the initial phases of the three clocks are: $\psi_{3}(0^{-})=\psi_{3}^{0}>\psi_{2}(0^{-})=\psi_{2}^{0}>0^{-}=\psi
    _{1}(0^{-})=\psi_{1}^{0}$.

3.  \[work4\]The perturbation satisfies the relation $P\left(
    x+Px\right)  \simeq Px$ in first order.

To obtain the desired model, we need to proceed through 6 steps, starting from the following initial conditions, that is the phase differences of all pairs of clocks.

In the sequel ${\psi}_{i}^{j}$ denotes the phase of clock $O_{i}$ at the $j-th$ step.

**INITIAL CONDITIONS**

The phase difference between $O_{3}$ and $O_{1}$ is $$(CA)_{0}={\psi}_{3}^{0}-{\psi}_{1}^{0}={\psi}_{3}^{0},$$ and the phase difference 