SP-120 System with Rudder Feedback - No Drive Unit The SP-120 autopilot control system comprises the following units:SP-120 display and control headSI-TEX 9 Axis rate compassRudder Feedback Unit (SP-120R only)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 the SP-120. A rudder actuator system comprises one of the following:Hydraulic system with helm pump and ramMechanical steering systemThe autopilot should be connected to one of the following:Reversing motor/pump set connected into the existing hydraulic steering systemReversing mechanical drive unit connected to the existing steering mechanismElectronic Hydraulic Solenoid Valves