  An exactly solvable model for a quantum measurement is discussed, that
integrates quantum measurements with classical measurements.
  The z-component of a spin-1/2 test spin is measured with an apparatus, that
itself consists of magnet of N spin-1/2 particles, coupled to a bath. The
initial state of the magnet is a metastable paramagnet, while the bath starts
in a thermal, gibbsian state. Conditions are such that the act of measurement
drives the magnet in the up or down ferromagnetic state, according to the sign
of s_z of the test spin.
  The quantum measurement goes in two steps. On a timescale 1/\sqrt{N} the
collapse takes place due to a unitary evolution of test spin and apparatus
spins; on a larger but still short timescale this collapse is made definite by
the bath. Then the system is in a `classical' state, having a diagonal density
matrix. The registration of that state is basically a classical process, that
can already be understood from classical statistical mechanics.
