  The DIRAC spectrometer has been commissioned at CERN with the aim of
detecting $\pi^+ \pi^-$ atoms produced by a 24 GeV/$c$ high intensity proton
beam in thin foil targets. A challenging apparatus is required to cope with the
high interaction rates involved, the triggering of pion pairs with very low
relative momentum, and the measurement of the latter with resolution around 0.6
MeV/$c$. The general characteristics of the apparatus are explained and each
part is described in some detail. The main features of the trigger system,
data-acquisition, monitoring and setup performances are also given.
