Bausch sold spectacles, thermometers, field glasses, magnifiers and opera glasses. The "microscopes" were simple magnifiers, not compound microscopes. Other rings had spinners, photo viewers, ballpoint pens, magnifiers, signal blinkers, flashlights, etc. Fresnel lenses are used as simple hand-held magnifiers. The reading room houses assistive devices such as print magnifiers and scanners with voice output. This value of the magnifying power is the one normally used to characterize magnifiers. We usually require special glasses or magnifiers in order to read. Screen magnifiers can be especially helpful for people suffering from low vision, including elderly users. Similar to desktop video magnifiers, this technology assists people with low vision. These include large print books and electronic magnifiers. High power magnifiers are sometimes mounted in a cylindrical or conical holder with no handle. Still finer steps can be found in low-cost plastic "sheet" magnifiers.