A graphical illustration of the relationships between two-port network parameters and the signals in the network. A signal flowgraph is a network of directed branches that are interconnected at nodes. The nodes have node signals, such as current, voltage, and power waves, and the branches have branch transmittances that specify the relationships between the signals at the source and sink nodes. The flow of signals in the graph is governed by the following basic rules: the node signal flows along the branch only in the direction of the arrow, and is multiplied by the transmittance of that branch; a node signal is equal to the algebraic sum of all signals entering that node; the signal at a node is applied to each of the outgoing branches from that node. See also Mason’s rules.