Braille cells are not the only thing to appear in braille text. Braille is a system of raised dots formed into units called braille cells. Fully contracted braille is known as "Grade 2 Braille". Such devices could include printers, speakers, monitors or a Braille embosser. Most institutions which produce Braille materials distribute BRF files. The Punjabi Braille is used by the visually impaired. There is no regular mapping to the braille ASCII numbering. A braille embosser is, simply put, a printer for braille. Their acute sensitivity provides the neural basis for reading Braille text. Braille literacy is a social-justice issue. Software is available that can print scores in braille. Some books are available in Braille and others in large print. Taiwanese braille is based on different letter assignments than Mainland Chinese braille. For blind people there is also a Guarani Braille. There are three levels of complexity in English Braille.