  The HEGRA--collaboration is operating a system of imaging atmospheric
Cherenkov telescopes to search for sources of TeV-gamma-rays. Air showers are
observed in stereoscopic mode with several telescopes simultaneously. To
trigger the telescope system a versatile two-level trigger scheme has been
implemented, which allows a significant reduction of the energy threshold with
respect to single telescopes. The technical implementation of this trigger
scheme and the performance of the trigger system are described. Results include
the dependence of single- and multi-telescope trigger rates on the trigger
thresholds, on the orientation of the telescopes, and on the type of the
primary particle.
