A prosthetic aid for a developing blind child

An experimental ultrasonic sonar for use as a sensory aid with blind children is described. Novel signal processing techniques make the aid relatively simple to construct, yet allow many of its parameters to be changed in the field. In particular, the aid has two features, a variable range code and an automatic level control, which make the device very versatile in a wide variety of environments. The ultrasonic tranducers used in the aid are described in some detail.