In this paper we study limits of generalized state space systems under
high gain feedback module system equivalence. Different group actions
on the space of system pencils are considered and related to the acti
on of pencil equivalence. A recent result on the orbit closure problem
for pencils is applied to obtain necessary conditions for a system to
be a limit of a given system under high gain feedback. These conditio
ns are shown to be sufficient for arbitrary state space systems. The r
esult is used to investigate a high gain version of Rosenbrock's probl
em: invariant factor assignment in the limit via high gain state feedb
ack.