  In this work we give a concise definition of information loss from a
system-theoretic point of view. Based on this definition, we analyze the
information loss in static input-output systems subject to a continuous-valued
input. For a certain class of multiple-input, multiple-output systems the
information loss is quantified. An interpretation of this loss is accompanied
by upper bounds which are simple to evaluate.
  Finally, a class of systems is identified for which the information loss is
necessarily infinite. Quantizers and limiters are shown to belong to this
class.
