Bell was born into an acoustic family in England and later moved to America. In Boston, a school has increased the number of deaf teachers. For professional reasons, he studied the physiological functions of listening and speaking. Later, he was hired as a professor of sound physiology at Boston University. 1873 resigned as a professor and began to concentrate on the research and development of telephones. To develop the telephone, we must first turn the sound signal into an electrical signal, and then turn the electrical signal into a sound signal. Before Bell, many people had been studying this problem. 1875, Bell was inspired by the application of electromagnets in telegraphy, which can convert electrical signals and mechanical movements. Bell began to design electromagnetic telephones. He first put a tuning fork in front of a coil with an iron core. The vibration of the tuning fork causes the iron core to move correspondingly, resulting in induced current. The current signal is transmitted to the other end of the wire and converted into a sound signal. Later, Bell changed the tuning fork into a metal piece that can vibrate with the sound, and changed the iron core into a magnetic rod. After repeated experiments, a practical telephone device was made. 1876, Bell obtained the telephone patent in the United States. He not only invented the telephone, but also established the first telephone company in the world.