Rotate-and-pull mechanisms for fiber optic modules. A degaussing current flowing to the degaussing coils has a waveform such that a line connecting a peak A from where a maximum current value first starts to decrease and a peak G of a sixth cycle is a functional curve of a second degree or greater. At least one document is selected from a collection of documents to be clusters. The GUI can concurrently provide a plurality of modes of operation for a plurality of playlists in a graphical framework.