Level-1 and level-2 triggering at LHC

The design of level-1 and level-2 trigger systems for future colliders is discussed. The constraints on the design of the trigger due to the collider parameters, the background rates, and large general-purpose detector designs are reviewed, and the problems of implementing a multi-level trigger system are addressed. Some examples of level-1 and level-2 trigger architectures are given for a variety of trigger signatures: high-pT electrons, photons and jets, large missing transverse energy, and high-pT muons.