  It is shown that Quantum Mechanics is ambiguous when predicting relative
frequencies for an entangled system if the measurements of both subsystems are
performed in spatially separated events. This ambiguity gives way to unphysical
consequences: the projection rule could be applied in one or the other
temporal(?) order of measurements (being non local in any case), but symmetry
of the roles of both subsystems would be broken.
  An alternative theory is presented in which this ambiguity does not exist.
Observable relative frequencies differ from those of orthodox Quantum
Mechanics, and a {\it gendaken} experiment is proposed to falsify one or the
other theory. In the alternative theory, each subsystem has an individual state
in its own Hilbert space, and the total system state is direct product (rank
one) of both, so there is no entanglement. Correlation between subsystems
appears through a hidden label that prescribes the output of arbitrary
hypothetical measurements. Measurement is treated as a usual reversible
interaction, and this postulate allows to determine relative frequencies when
the value of a magnitude is known without in any way perturbing the system, by
measurement of the correlated companion.
  It is predicted the existence of an accompanying system, the de Broglie wave,
introduced in order to preserve the action reaction principle in indirect
measurements, when there is no interaction of detector and particle. Some
action on the detector, different from the one cause by a particle, should be
observable.
