“…High luminosity operation, whether at a collider or with a fixed target, demands complex first level triggers with two relatively new characteristics: pipelined architecture, in order to avoid deadtime during the latency of the first level trigger, and very sophisticated, selective algorithms, in order to suppress high rate backgrounds. The calorimeter trigger electronics under development for the CMS detector [ 19] exemplifies these characteristics, first in the use of detailed Monte Carlo studies to establish physics requirements and to study trigger selection algorithms, and then in its use of state-of-the-art electronics, such as custom GaAs integrated circuits, gigabit per second fiber optics, and 160-MHz point-to-point backplanes. Development of first level triggers for HERA-B [20] and STAR [2l] were also reported.…”