Why does there need to be a special player for talking books?
Most ordinary cassettes play for sixty to ninety minutes. Using the special four-track, half-speed NLS format, a tape that would normally play only ninety minutes can play for six hours. The additional playing time helps save money on the number of cassettes and makes books easier to use. Also, the NLS format makes the books unusable by the public, a requirement under the U.S. copyright law that permits NLS free use of copyrighted material.
