作业帮英语作文不会写
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英语作文不会写
英语作文不会写
英语作文不会写
When Bell began experimenting with e lectrical signals, the telegraph had bee n an established means of communica tion for some 30 years. Although a hig hly successful system, the telegraph, w ith its dot-and-dash Morse code, was basically limited to receiving and sendi ng one message at a time. Bell's exten sive knowledge of the nature of sound and his understanding of music enable d him to conjecture the possibility of tr ansmitting multiple messages over the same wire at the same time. Although the idea of a multiple telegraph had be en in existence for some time, Bell offe red his own musical or harmonic appr oach as a possible practical solution. H is "harmonic telegraph" was based on the principle that several notes could b e sent simultaneously along the same wire if the notes or signals differed in pitch.