(Reprinted in 1992 in {\em MIC}, see paper 33 in list of journal publications)

**Abstract.**
Decentralized controllers (single-loop controllers applied to
multivariable plants) are often preferred in practice because they are
robust and relatively simple to understand and to change. The design
of such a control system starts with pairing inputs (manipulated
variables) and outputs (controlled variables). For a *n*x*n*
plant there are *n*! possible pairings, and there is a great need
for screening techniques to quickly eliminate undesirable pairings. In
this paper we present several tests for eliminating pairings which are
not decentralized integral controllable (DIC). A system is DIC if
there exists a stabilizing decentralized controller with integral
action such that the gains of the individual loops may be reduced
independently without introducing instability. Note that DIC is a
property of the plant and the chosen pairings. The tests presented are
in terms of different measures of the sign of steady state gain
matrix; including the RGA, the determinant and eigenvalues. The
relationship to previously presented results is discussed in detail.