A scan-to-scan integrator for use in radar apparatus comprises means for defining a search window for use in verifying a candidate detection. The location information is generated by using branch identifiers, each of the branch identifiers being allocated for each branch from a root node to a target node. The photoimageable material is exposed to actinic radiation, except for an area corresponding to the aperture in the top layer. The state includes a state in which the engine is not running. The holder has a first retention member including a back plate, a first retention guide connected with an end of the back plate and a second retention guide connected with an opposing end of the back plate.