See my reply to your previous post:-
"Older electro hydraulic steering gears tended to use Helie Shaw / tilting swashplate pumps. These pumps could vary the the output of the pump from 100% in one direction, through zero to 100% in the other direction.
More modern pumps deliver a fixed flow of oil to a solenoid valve. With power off the solenoid valve the oil recirculates through the pump. When either the Port or Starboard solenoid coils are energised oil is delivered from the valve, moving the steering gear in that direction until the signal from a feedback potentiometer on the rudder equals the value of the desired value signal for rudder angle. The solenoid is then de-energised the spool of the solenoid valve is spring loaded back to the neutral position and the steering gear is hydraulically locked in position, untill either the rudder moves or the desired value changes.
Feedback for the control system is entirely electrical now adays, no more hunting gear or mechanical links, no more hydraulic servos, only electrical cable from the hand steering and autopilot to the solenoid valves and feedback potentiometers.
The valve block is usually mounted directly on top of the hydraulic pump, it usually consists of a spool valve with a solenoid at each end. The solenoids have push buttons or similar manual operating arrangements for emergency local control.
In normal operation the autopilot or Bridge manual steering wheel will send an electrical signal to the rudder control, indicating a "desired Value" for the rudder angle, the Potentiometer on the rudder gives a feed back of the actual or "Measured Value" of rudder angle. The control unit compares the 2 signals and energises the correct solenoid until the feed back signal matches the Desired Value signal. The solenoids are then de-energised, and the rudder remains hydraulically locked in that position. (It can only move if the Hydraulic safety valves lift, or there is air in the hydraulic system, (making it compressible).
I hope this clears matters up for you.
It is always better to ask a stupid question than to do a stupid thing.