Electrode and nozzle that seat within a retaining member and in two different seating locations relative to retaining member. The devices of a cluster share input and output ring segments such that packets arriving on the input segment are received and interpreted by all the devices in a cluster. The lamp is activated by rotating a fresnel lens about its longitudinal axis relative to the body. Also, an air purifier is mounted in the body casing. The facility identifies as most relevant those items having the highest ranking values. The recording layer includes a first chemical compound having a spinel structure.