An operator
![F[e, i]](/images/tex/11006.gif)
defined on

-port networks is said to satisfy the condition of edge-port conservation if it satisfies
![\\sum_{\\hbox {all the ports}} F[e_{m}, i_{m}] = \\sum_{\\hbox {all the edges}} F[\\upsilon _{k},j_{k}]](/images/tex/11007.gif)
where

are the voltage and current functions at the

th port and

are the voltage and current functions at the

th edge, respectively. It is shown that an operator satisfies the condition if and only if the operator is additive.