  Nowadays various chaotic secure communication systems based on
synchronization of chaotic circuits are widely studied. To achieve
synchronization, the control signal proportional to the difference between the
circuits signals, adjust the state of one circuit. In this paper the
synchronization of two Chua circuits is simulated in SPICE. It is shown that
the choice of control signal is be not straightforward, especially in the case
of multistability and hidden attractors.
