A group of network devices, such as Ethernet switches, are logically configured as a single cluster, with one commander device and one or more member devices. At least one reagent pad is provided by impregnating a first porous material with an aqueous solution including a reagent capable of reacting with the analyte, a derivative of the analyte or an indicator compound for the analyte to provide a detectable signal when in a moistened state. In a preferred embodiment of the present invention, an operator can grasp the plurality of needle electrodes that are mounted on a support structure and firmly insert the them into the selected tissue in a body or plant. Optionally, nutritional supplements or medicines may be added to the infused liquid. The invention can be usefully employed to adjust the frequency at which content-channel updates or content-catalog updates are transmitted to communication devices such as cellular wireless devices for instance. In some such embodiments, the second display area displays the entirety of the preview of the entire content at once.