We'll follow certain rules when we build up a network flow graph.

- Each variable and will be designated as a node.
- Each of the S-parameter will be a branch.
- Branches enter dependent variable nodes and emanate from the independent variable nodes.
- Each node is equal to sum of the branches entering it.

**Figure 10:** Complete Flow graph for 2-port

- Flow graph of a source
- Flow graph of a load
- Flow graph of a 2-port network with source and load
- Mason's rule