A magnetic raking device that agitates a ground surface and uses magnetic attraction for collecting ferro-metallic debris, such as nails and screws, at construction jobsites and other locations, includes a release mechanism that temporarily eliminates magnetic attraction of the debris to the rake, thus allowing collected debris to drop from the rake, such as into a trash or recycling container. The voltage controlled delay line may have a plurality of buffer stages to provide a first clock signal and a second clock signal. Thus, as the lifting arm pivots, the housing pivots in relation to the lifting arm and the bearing is kept vertical or substantially vertical. The point-spread function matrix includes information about the shape and relative position of the point-spread function of each spot to be exposed on the substrate by one of the sub-beams of radiation at a given time. Release of the algaecide is controlled by the structure of the granules. This protection scheme can be used in both uni- and bi-directional systems to provide protection for information being transmitted on one or more fibers or fiber paths.