Bell and his assistant Charles Sumner Tainter jointly invented a wireless telephone, named a photophone, which allowed for the transmission of both sounds and normal human conversations on a beam of light. Both men later became full associates in the Volta Laboratory Association.
బెల్ యొక్క కార్డ్-ఫ్రీ ఫోన్ సందేశాలను ప్రసారం చేయడానికి ఏమి ఉపయోగించింది?
light