Embodiments herein receive a set of content quality threshold values, a search string, and a content data stream at a content quality metric apparatus. When the convertible electrical device cover is placed in an operative position over the electrical device the adapter plate may be located between the electrical device and a rear side of the base plate. Each of the second optical waveguides is electromagnetically coupled to the first optical waveguide exactly once, and each of the closed loops has a round trip time. The open cavity can be configured to allow the system to act as a spring. Each projection includes metal powder at portion in contact with the through hole to provide good electrical connection.