Chorded keyboard (a writing system for the blind) uses either 6 or 8 tactile 'points' from which all letters and numbers are formed. When Louis Braille invented it, it was produced with a needle holing successively all needed points in a cardboard sheet. In 1892, Frank Haven Hall, superintendent of the Illinois Institute for the Education of the Blind, created the Hall Braille Writer, which was like a typewriter with 6 keys, one for each dot in a braille cell. The Perkins Brailler, first manufactured in 1951, uses a 6-key chord keyboard (plus a spacebar) to produce braille output, and has been
The blind leading the blind The blind leading the blind "The blind leading the blind" is an idiom and a metaphor in the form of a parallel phrase, it is used to describe a situation where a person who knows nothing is getting advice and help from another person who knows almost nothing. It can be traced back to the Upanishads, which were written between 800 BCE and 200 BCE. A similar metaphor exists in the Buddhist Pali Canon, composed in North India, and preserved orally until it was committed to writing during the Fourth Buddhist Council in Sri Lanka in 29 BCE. The expression