A traction apparatus for cervical vertebrae for elongating the cervical vertebrae with the cervical vertebrae being stooped in response to the manipulation of a user. The clippers are retained side-by-side in one compartment separated by partitions from other compartments containing other barber’s accessories. An absorption coefficient for the absorptive material may be determined based on the first and second light intensities measured when the cavity is illuminated by a light source. Thus, embodiments of the present invention allow a maximum data rate that can be sustained on a DSL loop without an excessive quantity of errors. By appropriately designing the optical system, the variable focal-length lenses or mirrors can provide the flexibility necessary to change the overall system focal length, and therefore magnification, that is normally accomplished with mechanical motion in conventional zoom lenses.