1. An oximeter, comprising: a plurality of processing modules, each responsive to a noninvasive sensor signal indicative of light attenuated by body tissue, at least one processing module having different characteristics from another processing module, each of said plurality of processing modules outputting a parallel measurement, an alarm; a memory storing criteria indicative of alarm conditions, said criteria including at least a duration of at least one of said parallel measurements crossing a threshold; an alarm indicator receiving said parallel measurements from said plurality of processing modules, extracting features from said parallel measurements, comparing said features to said criteria, and when said features match said criteria, triggering said alarm on said oximeter.