  We give a complete characterization of the possible response matrices at a
fixed frequency of n-terminal electrical networks of inductors, capacitors,
resistors and grounds, and of n-terminal discrete linear elastodynamic networks
of springs and point masses, both in the three-dimensional case and in the
two-dimensional case. Specifically we construct networks which realize any
response matrix which is compatible with the known symmetry properties and
thermodynamic constraints of response matrices. Due to a mathematical
equivalence we also obtain a characterization of the response matrices of
discrete acoustic networks.
