Telephone introduction
Telephone English, telephone, originated from Greek, is a kind of remote communication equipment that can send and receive sounds. As early as the eighteenth century, the word telephone was used in Europe to refer to a microphone made of string. The telephone was attributed to Alexander Graham Bell. The principle of early telephone is that sound is a compound vibration in the air, which can be transmitted to solids and to conductive metals through electric pulses.
The telephone was invented by American AG Bell Company in 1876. He used two wires to connect two transmitters and receivers with the same structure, and the electromagnet was equipped with a diaphragm, so that the two ends could talk at the beginning. But the call distance is short and the efficiency is low. Carbon microphone appeared in 1878, which greatly improved the efficiency of telephone microphone. The receiver structure has also been improved. The earliest telephone was a magnet telephone, which was powered by its own battery and sent a call signal with a hand-cranked generator.