The U. S. patent granted to Alexander Graham Bell in 1876 for developing a device to transmit speech sounds over electric wires is often called the most valuable ever issued.
1876年贝尔发明了一种装置，能在电线上传送声音，并获得了美国专利，人们往往称这个发明是最有价值的。
The U. S. patent granted to Alexander Graham Bell in 1876 for developing a device to transmit speech sounds over electric wires is often called the most valuable ever issued.
1876年贝尔发明了一种装置，能在电线上传送声音，并获得了美国专利，人们往往称这个发明是最有价值的。
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