A microphone depending for its action on the varying electrical resistance of carbon granules when subjected to the varying pressure of sound waves.
Late 19th century; earliest use found in Telegraphic Journal.
英语词典包含464360条英英释义在线翻译词条，基本涵盖了全部常用单词的英英翻译及用法，是英语学习的有利工具。