Servo Unit

The servo unit is essentially a vacuum activated variable diaphragm. It positions the throttle when the system is in operation through a bead chain actuator, combination chain and cable actuator or rod actuator depending on model of vehicle.
To operate the servo unit, a controlled vacuum provided by the servo unit solenoid valve is applied to the servo diaphragm, drawing the diaphragm inward, pulling the actuator to operate the throttle.