作业帮英语作文你认为最有用的发明
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英语作文你认为最有用的发明
英语作文你认为最有用的发明
英语作文你认为最有用的发明
The telephone is an instrument that converts voice and sound signals into electrical impulses for transmission by wire to a different location,where another telephone receives the electrical impulses and turns them back into recognizable sounds.In 1875,Alexander Graham Bell built the first telephone that transmitted electrically the human voice.
When Bell began experimenting with electrical signals,the telegraph had been an established means of communication for some 30 years.Although a highly successful system,the telegraph,with its dot-and-dash Morse code,was basically limited to receiving and sending one message at a time.Bell's extensive knowledge of the nature of sound and his understanding of music enabled him to conjecture the possibility of transmitting multiple messages over the same wire at the same time.Although the idea of a multiple telegraph had been in existence for some time,Bell offered his own musical or harmonic approach as a possible practical solution.His "harmonic telegraph" was based on the principle that several notes could be sent simultaneously along the same wire if the notes or signals differed in pitch.
The telephone is an instrument that converts voice and sound signals into electrical impulses for transmission by wire to a different location, where another telephone receives the electrical