Nontriviality of Siddiqi class on the arc of bounded slope

We study a problem of incompleteness of the system of exponentials $\{e^{\pm \lambda_n z}\}$ $(\lambda_n>0)$ in the space of continuous functions on the arc of bounded slope. In the terms of minorant sequence we have obtained a new equivalent condition of nontriviality of Siddiqi class which is sufficient for incompleteness of the given system of exponentials.