Features are disclosed for measuring and correcting clock drift and propagation delay in an audio system through one or more waveforms embedded in an audio signal. The tool includes: a replaceable, expandable head for insertion within an end of the pipe; and a gripping and pressing member to grip the fitting and the retaining sleeve and to press the retaining sleeve over the pipe and fitting. At least a first portion of the lead body, proximal to the electrodes, is transparent or translucent and at least a second portion of the lead body, separating two or more of the segmented electrodes, is opaque so that the segmented electrodes separated by the second portion of the lead body are visually distinct. The indoor mobile unit positioning includes mobile unit-based positioning which makes use of reception of access point signals by the mobile unit. The method may then determine a distance from each of the plurality of patches to its corresponding similar patch and select a crop in the first image relative to the second image based on the determined distance.