Status and Design of CMS Level 1 Trigger System

We present the design and status of the Level 1 trigger system for the Compact Muon Solenoid (CMS) detector at the Large Hadron Collider (LHC). The CMS Level 1 trigger system contains a Calorimeter Trigger, a Muon Trigger and a Global Trigger. Its purpose is to reduce the event rate from the 40 MHz crossing rate to a maximum output rate of 30 kHz. This maximum rate is estimated by appling a conservative safety margin to the maximum input rate tolerable to the higher level trigger system (100 kHz).