... devised the sign language used by the hearing impaired.

Jerome Cardan devised the sign language. Deaf and mute people faced unreasonable brutality at one point of time. Jerome Cardan was an Italian doctor who believed that the mute and deaf people could be taught to communicate by using written characters. Finger characters were worked out for them in the seventeenth century which was very similar to the present-day finger alphabets. About seventy five years ago the deaf were taught to communicate ideas almost entirely by means of signs, facial expressions and finger alphabets.