Process Make Call with Telephones

What if you want to talk right now to a friend who lives far away? The answer is simple. You pick up your telephone and press some buttons. Next, you hear a ringing sound-one, two, three rings. Then you hear your friend's voice say, "Hello". Making a phone call seems so easy. But did you ever think about what makes it possible?

When you talk on the phone, your voice is changed into an electric signal that can travel through wires. A plastic disk in the mouthpiece vibrates when you speak. The vibration makes a pattern in an electric field between the plastic disk and a metal disk. The pattern is sent through wires as an electric signal. Just as a telephone can turn a voice into an electric signal, it can also change an electric signal back into a voice. When the signals pass through magnets in the earpiece, the magnets vibrate a disk that reproduces the speaker's voice.

When you make a local call, the call travels over wires from your house to the telephone company's routing station. From there, a computer automatically sends the call to the number you dialed. Did you know you can call someone on other side of the world? The call might even be sent into space! Satellites orbiting high above Earth connect calls between distant countries. Some international calls travel along cables under the sea. Cell phones work by sending a radio signal through the air to a cell tower. The tower sends the signal to the cell phone company, which relays it to another cell phone or through the telephone company to a wired phone.