Evaluation and a Method of Presentation of the Sound Output From the Lexiphone-A Reading Machine for the Blind

The operation of the Lexiphone, a reading machine for the blind, is described. The Lexiphone produces a sound pattern for each of the alphabet symbols, and the blind reader has to learn to associate each of these patterns with the corresponding letter. With practice, whole words and short phrases are recognized as entities. As the Lexiphone machine reads each line of print by scanning it with a column containing a large number of photodiodes (54), the visual resolution is quite high and the equivalent quantizing noise is low The signals from the photocells are processed by digital circuits to. produce the modulating signals of a single square wave. The square wave is modulated both in frequency and amplitude, the frequency component being the chief one to identify the letter, and the code sounds generated by the machine reported to be quite pleasant. The physical construction of the Lexiphone is robust and a description of the machine is given. The reading speed of the Lexiphone is discussed. Experiments indicate that a reading speed of over 30 words a minute including line change can be attained with 200 h of training (over a year). A method of dichotic presentation has been proposed to increase the reading speed and preliminary experiments have produced encouraging results.