The present invention relates generally to the field of mounting devices for audio and visual components, and more specifically to an apparatus for displaying associative images and maximizing their cognitive effect on a user. The MUX circuit includes multiple current control elements, which each include multiple inverters coupled to a transmission gate. Various aspects of the residential fire sprinkler, including a method of protecting a residential dwelling unit are described. A controller utilizes a database of test recipes to supervise and control the optical signal sources, optical signal degradation elements, units under test, input switches, output switches, and test equipment to conduct a variety of optical tests on the modules.