"专用功能部件" can be translated as "dedicated functional unit" or "special-purpose functional component" in English.
"Dedicated" emphasizes that the unit is designed for a specific purpose or task.
"Functional" indicates that it has a specific function or role.
"Unit" or "component" refers to a part or module within a larger system.
Both translations are acceptable, and the choice between them may depend on the specific context or the preferred terminology in the relevant field.