The trigger system of the HESS telescope array

H.E.S.S. - The High Energy Stereoscopic System - is a new system of large atmospheric Cherenkov telescopes for GeV/TeV gamma-ray astronomy. This paper describes the trigger system of H.E.S.S. with emphasis on the multi-telescope array level trigger. The system trigger requires the simultaneous detection of air-showers by several telescopes at the hardware level. This requirement allows a suppression of background events which in turn leads to a lower system energy threshold for the detection of gamma-rays. The implementation of the H.E.S.S. trigger system is presented along with data taken to characterise its performance. (C) 2004 Elsevier B.V. All rights reserved.