Fig. 13 Basic closed-loop diagram of the dual-mode version subsystem (heavy lines) with open-loop vestibular inputs (heavy lines) superimposed on the block diagram of the total ocular motor control system. The retinal error inputs combine with head acceleration and position inputs to create all version outputs (FEM, SEM, and FEM plus SEM). See Figures 7, 9, and 11 for explanations of the individual components of the version subsystem.