Nonlinear planar response of a cable under plannar narrow band radom excitation is studied.A response equation for the mean square deflection is obtained under a single mode approximation by using the equivalent linearization technique.It is shown that the response is triple valued,if the center frequency of excitation lies in a certain specified range.The triple valued response occure only if the excitation of excitation lies in a certain specified range.The triple valued response occures only if the excitation bandwidth is smaller than a critical value which is monotonically increasing function of the intensity of excitation.