SI-TEX SP-120 Color System w/Virtual Feedback - No Drive Unit [SP120C-VF-1]SP 120 Color System with Virtual Feedback No Drive Unit The SP 120 autopilot control system comprises the following units: SP 120 display and control head SI TEX 9 Axis rate compass In addition the SP 120 has to be connected to a drive unit which controls the rudder actuator system in order to complete the full autopilot system. The actuator system provides the physical movement to the rudder responding to the direction of control signals provided by