Effects of a vanishing variable on the signal-flow graph

TLDR: Two rules are derived to reduce a signal-flow graph when one of the node variables vanishes, which render immediate uses in obtaining network parameters.

Abstract: Two rules are derived to reduce a signal-flow graph when one of the node variables vanishes. Since the vanishing of a node variable in the flow graph of a network corresponds to either opening or short-circuiting a specific network branch, the derived rules render immediate uses in obtaining network parameters.