Strange attractors in a system described by nonlinear differential-difference equation

The phenomena of strange attractors, which occur in a system described by a differential-difference equation representative of phase-locked loops (PLL) with time delay, are treated. Synchronized states of the PLL are represented by the equilibrium points of the equation. The pull-in region, i.e. the parameter region in which all initial conditions lead to quiescent steady states, has been reported by Ueda (1981). A survey is given of various types of steady states, especially chaotic steady states, in computer-simulated systems of the equation.