Which component allows for hydraulic control of the steering system?

The trick wheel is a component that allows for hydraulic control of the steering system by converting the mechanical input from the operator into hydraulic pressure. This mechanism is designed to provide more precise control over the ship's steering, as it utilizes hydraulic fluid to transmit forces that adjust the rudder's position.

When the operator turns the trick wheel, it activates hydraulic valves that adjust the flow of hydraulic fluid to the steering actuators. This allows for smoother steering responses and the ability to handle the ship effectively, especially during complicated maneuvers or adverse sea conditions. The trick wheel serves as a vital interface between the operator and the hydraulic systems that dictate the vessel's direction.

Each of the other choices serves different functions within the steering and control systems. The differential control box helps manage the output signals to various devices but does not directly enable hydraulic control. The emergency steering pump serves as a backup in the event of a primary system failure, while the RAM actuator's role is to physically move the rudder based on hydraulic pressure. However, the critical action of controlling steering through hydraulic means is primarily attributed to the trick wheel.