The topological implications of irreducibility of the admittance or impedance matrix of an n-port network are studied. Special attention is given to the cases when in

rows of such a matrix of order

the main diagonal elements are equal to the absolute values of some off-diagonal elements. It is shown that the conditions of realizability of a

or

matrix of this type reduce to the known conditions of realizability by means of a network with

vertices or exactly n independent circuits. Some examples show realizable

matrices which cannot be realized as

matrices and vice versa. Other examples give nonrealizable, paramount

and

matrices showing that paramountcy is not a sufficient condition for realizability.