  The Liquid Argon Jet Trigger, installed in the H1 experiment at HERA,
implements in 800 ns a real-time cluster algorithm by finding local energy
maxima, summing their immediate neighbors, sorting the resulting "jets" by
energy, and applying topological conditions. It operated since the year 2006
and drastically reduced the thresholds for triggering on electrons and jets.

Instrumentation and Detectors;High Energy Physics - Experiment