There is disclosed a sensor and method for detecting very low frequency acoustic signals. The simulation may then be continued after the performance of the activity has ceased. The compression-resultant signal is formatted into a formatting-resultant signal corresponding to a predetermined format for a digital recording disc. Alternatively, an outlet diffuser may be provided at the display screen to complement the inlet diffuser by differently diffusing the image light spatially at the display screen. Logic gates and logic functionality employing an optical switch are also described. The first portion can be threaded into a suture anchor such that it can be doubled over upon itself.