What type of diagram illustrates the external connections between all system devices and components?

The interconnecting diagram is specifically designed to show how different system devices and components connect with each other externally. This type of diagram provides a clear visual representation of the relationships and connections between various elements within a system, making it easier for technicians and engineers to understand the layout and functionality of the overall system.

In contrast, a wiring diagram typically focuses on the physical wiring connections and layout of circuits, but may not depict the overall connectivity between components as clearly as an interconnecting diagram. Ladder diagrams are primarily used for illustrating control circuits in a way that resembles a ladder, emphasizing relay logic rather than external connections. Schematic diagrams are valuable for showing the electrical functions and relationships within a circuit but do not usually focus on the external connections between components.

Thus, the interconnecting diagram serves as the most appropriate choice for illustrating the external connections between all system devices and components.