For example, a telephone call may travel by means of copper wire, fiber-optic cable, and radio waves as the call is sent from sender to receiver.
例如，电话中的通话从讲话人传送到听话人，其间可能要通过铜线、光缆和无线电波进行传输。
A device that converts electric signals, as from a telephone, stereo, or radio receiver, to audible sound and fits over or in the ear.
耳机一种传递电子信号的设备，比如从电话、立体声或广播接收器上传出可听的声音。这种设备嵌到耳朵上或耳朵里。
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