The level-1 global trigger for the CMS experiment at LHC

The electronics of the First Level Global Trigger for CMS electronics is described. It is the last stage of the Level-1 trigger system and decides for every LHC bunch crossing whether to reject or to accept a physics event for further evaluation by the High Level Trigger. The Global Trigger receives trigger objects from the Global Calorimeter Trigger and the Global Muon Trigger and applies in parallel up to 128 physics trigger requirements, so-called ‘Algorithms’. In addition, up to 64 so-called ‘Technical Trigger’ signals can be used to either accept or reject events. The Algorithm and Technical Trigger bits are then combined to a Final_OR signal to start the readout procedure of an event.