This document describes systems, devices, and methods that use multiple morphology templates for discriminating between rhythms, such as supraventricular tachyarrhythmias and ventricular tachyarrhythmias, for delivering a countershock in response to a VT episode, but withholding delivery of such a countershock in response to an SVT episode. An internal dummy electrode is provided around a region where the exposed ends of the plurality of internal electrodes are distributed in the WT surface of the component main body. In this way an integral reading light with a forced-air nozzle, or an integral forced-air nozzle with a reading light, is implemented that uses little design space. Means for moving reciprocally a base material having conductivity in opposite direction is provided. The sprocket may be shifted between a first orientation in which the shank may be rotated while the sprocket is secured against rotation to adjust the height of the appliance by translatory movement of the shank and a second orientation in which the sprocket may be rotated and the shank is secured against rotation but is free to move axially.