CMS calorimeter trigger circuits

The CMS level 1 trigger decision is based in part upon local information from the level 1 calorimeter trigger about the presence of objects such as photons, electrons and jets, as well as global sums of E/sub t/ and missing E/sub t/ (to find neutrinos). The electron/photon trigger is based on the recognition of a large and isolated energy deposit in the electromagnetic calorimeter by asking for a small hadronic energy deposited in the HCAL in the cluster region. We present a description of the calorimeter regional trigger crates, the receiver card, the electron isolation card and the jet summary card.