  The DISTO collaboration has built a large-acceptance magnetic spectrometer
designed to provide broad kinematic coverage of multi-particle final states
produced in $pp$ scattering. The spectrometer has been installed in the
polarized proton beam of the Saturne accelerator in Saclay to study
polarization observables in the $\vec{p} p \to p K^{+} \vec{Y}$ ($Y = \Lambda,
\Sigma^{0}$ or $Y^{*}$) reaction and vector meson production ($\phi, \omega$
and $\rho$) in $pp$ collisions.
  The common signature of such events is the multiplicity of four charged
particles in the final state.
  A flexible 1st level trigger which uses topological information from fast
detectors (scintillating fibers and hodoscope) has been built.
  It is completely software programmable through a menu-driven user interface
and allows switching between production and monitor triggers on successive beam
spills.
