In the design and architecture of complex systems, various types of diagrams and visual representations are commonly used to communicate technical details, relationships, and structures effectively. Here are some of the key types of diagrams often employed in technical design and architectural planning:

1. Flowcharts: Flowcharts are used to represent the flow of processes or workflows within a system. They use shapes and arrows to illustrate the sequence of steps, decision points, and interactions between components.

2. UML Diagrams: Unified Modeling Language (UML) diagrams are a standardized set of diagrams used in software engineering. They include class diagrams (showing class relationships), sequence diagrams (depicting interactions between objects over time), and use case diagrams (describing system functionality).

3. Entity-Relationship Diagrams (ERDs): ERDs are used in database design to model data structures and the relationships between entities (tables) in a database system. They help define the schema for databases.

4. Architectural Diagrams: These diagrams provide an overview of the high-level architecture of a system. They show the main components, their interactions, and how data flows between them. Common types include block diagrams and system architecture diagrams.

5. Network Diagrams: Network diagrams depict the layout and connections of network infrastructure components, such as routers, switches, servers, and client devices. They help in planning and managing network configurations.

6. Data Flow Diagrams (DFDs): DFDs illustrate the flow of data within a system, highlighting processes, data sources, data sinks, and data transformations. They are used for system analysis and design.

7. State Diagrams: State diagrams model the behavior of a system or component by showing the various states it can be in and the transitions between those states. They are especially useful for modeling complex, stateful systems.

8. Component Diagrams: Component diagrams display the physical and logical components of a system or software application. They show how these components interact to provide specific functionalities.

9. Deployment Diagrams**: Deployment diagrams are used to visualize the physical deployment of software components on hardware nodes. They help in planning the distribution and scaling of software systems.

10. Timing Diagrams: Timing diagrams are used to depict the timing and duration of interactions or events within a system. They are particularly valuable for real-time and embedded systems design.

11. Block Diagrams: Block diagrams provide a high-level view of a system, showing major functional blocks or modules and their connections. They simplify complex systems for better understanding.

12. User Interface (UI) Wireframes: UI wireframes are sketches or diagrams that outline the layout and structure of user interfaces. They help in designing and prototyping user-friendly software applications.

These diagrams serve as powerful tools for architects, engineers, and designers to plan, communicate, and document technical systems effectively. The choice of which diagram to use depends on the specific needs of the project and the level of detail required to convey complex technical information.