Alexander Graham Bell was credited for having invented the telephone on March 10, 1876. It was a magnificent invention, that helped us in so many ways. It is only proper that we give proper recognition to this device by trying to understand how it functions. But we would not go to the extent of explaining acoustics or the science of sound to make our point.
First let us define telephone as a device capable of replicating voice and transmitting it from one point to another in the fastest means possible. Imagine, we can now hear the replicated voice of our relatives on the other side of the planet in a matter of seconds through telephone wires. Yes, the voice we hear on the phone is a product of replication by devices.
Let us try to define some terms in simple language. Human voice is a sound, which is produced by the movement or vibration of our lips, tounge and mouth. Sound wave travels through the air, water or solid objects. It is important to realize that sound can be converted into electrical energy, which we will elaborate later. Telephone is a device that can transform sound into electrical energy and transmit it through copper wires to another point.
Remember that as grade school children, we had for a school project a basic telephone, composed of two cans connected by a string. When we pull the string to form a straight line and make it tight, we can actually communicate through the cans. This is possible because when one student talks into the can, the bottom of the can vibrates back and forth with sound waves that travel through the straight line of string, which the other student who puts his ear near the can hears. The telephone uses the same principle, but instead of string, it uses wire.
Instead of empty cans, the telephone uses a mouthpiece, composed of a transmitter, which is made up of a thin metal diaphragm. Inside the diaphragm is a small chamber filled with carbon granules. When we speak, sound waves cause the granules to compress, which allows a low-voltage electric current to pass. This current comes from batteries at the telephone company. The electric current then travels. The louder we speak, the more the granules are compressed, and the heavier voltage of electric current is released. When the carbon grains are compressed, electric currents pass through them more easily. If we don't make any sound, no sound waves will cause the grains to compress, which would not allow electric currents to pass.
By copying the pattern and loudness of our voice, the release of the electric current through the carbon grains serves as the same pattern when the current hits the diaphragm on the other line. In other words, the vibrations caused by our voice are converted into electrical impulses that travel through wires until they reach the receiver. The receiver (ear-piece), which also has an iron diaphragm, converts the electrical impulses back into sound. Once the electric current hits the electromagnetic field in the receiver, the diaphragm vibrates and produces sound waves almost exactly like the pattern of sound waves at the point of origin.
Simply put, the telephone set has transmitter, receiver, a connection and a switch, which allows us to dial a number and exchange replicated voices.