  In this work, we push further the analysis of the problem of switching
controls proposed in [E. Zuazua, Switching control, J. Eur. Math. Soc. (JEMS),
13(1): 85--117, 2011]. The problem consists in the following one: assuming that
one can control a system using two or more actuators, does there exist a
control strategy such that at all times, only one actuator is active? We answer
positively to this question when the controlled system corresponds to an
analytic semigroup spanned by a positive self-adjoint operator which is
null-controllable in arbitrary small times. Similarly as the argument of E.
Zuazua, our proof relies on analyticity arguments and will also work in finite
dimensional setting and under some further spectral assumptions when the
operator spans an analytic semigroup but is not necessarily self-adjoint.
