Abstract: This invention relates to clinical diagnostic assays and related optical bio-discs and a disc-reading apparatus. The invention is directed to a methods for determining the blood cell type of an individual.

Abstract: A secondary surveillance radar is arranged to monitor the relative amplitudes of sum signals and difference signals received from a target in response to interrogations. Only those replies for which the sum signal exceeds the difference signal by a predetermined amplitude are accepted as valid to avoid degradation of the performance of the radar due to "punch through". "Punch through" stems from distortions in the radiation pattern of the radar and is often caused by reflections of the radar signals by large objects. A directional receiving antenna generates sum (.SIGMA.) and difference (.DELTA.) signals, and replies are accepted as valid and gated to an output only if a quantity log .DELTA./.SIGMA. exceeds a reference when compared at a comparator.