When the caller picks up the phone and speaks into the microphone, the vibration of the vocal cord excites the air to vibrate, forming a sound wave.
The sound waves act on the microphone to generate a current called a voice current.
The voice current is transmitted along the line to the receiver of the other party's telephone, and the receiver acts just the opposite of the microphone - converting the current into sound waves that pass through the air to the person's ear.
In this way, the simplest call process is completed.
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