On a type-reading optophone

Abstract

Abstract The production of sounds directly or indirectly due to the incidence of light is the general function of instruments of the type of Graham Bell's "photophone." An instrument designed to solve the more special problem of substituting the sense of hearing for the sense of sight is more appropriately termed an "optophone." Having concerned myself fro a number of years with this special problem, I described in 1912 an instrument which enabled sightless persons to locate bright lights or brightly luminous objects by means of the ear, and to discover shadows intercepting the light. This result was obtained by putting two selenium preparations into two arms of a Wheatstone bridge, sending the galvanometer current through a telephone, and interrupting the current by clockwork interrupter. A disadvantage of the method was that the action of the light was not instantaneous.