Recycle or reuse what materials you can. Already a subscriber? Sign in. Thanks for reading Scientific American. Create your free account or Sign in to continue. See Subscription Options. Go Paperless with Digital. Key concepts Sound Waves Hearing From National Science Education Standards : Transfer of energy Introduction Have you ever tried to have a conversation with someone so far away that you couldn't really hear each other? Read on for observations, results and more resources. Get smart. Sign up for our email newsletter.
Sign Up. Support science journalism. More sophisticated smart phones can perform similar functions of a portable computer. Cell phones use radio waves to communicate. Radio waves transport digitized voice or data in the form of oscillating electric and magnetic fields, called the electromagnetic field EMF. The rate of oscillation is called frequency. Radio waves carry the information and travel in air at the speed of light. Cell phones transmit radio waves in all directions. The waves can be absorbed and reflected by surrounding objects before they reach the nearest cell tower.
For example, when the phone is placed next to your head during a call, a significant portion over half in many cases of the emitted energy is absorbed into your head and body. A telephone is one of the simplest devices you have in your house. In fact, the telephone connection to your house has not changed in nearly a century.
If you had an antique phone from the s, you could connect it to the wall jack in your house and it would work fine. There are two essential parts to a telephone: the microphone which you talk into and the speaker which you put by your ear.
Inside the microphone is a thin piece of metal called a diaphragm. It vibrates when the vibrations from your voice hit it. As the diaphragm vibrates, it wiggles a magnet to make current flow down the wire. At the other end is a speaker.
A speaker has a permanent magnet and an electromagnet inside it. When electric current pulses flow through the electromagnet, it moves back and forth, attracted and repelled by the permanent magnet.
This makes a membrane vibrate, which creates sound. A switch to connect and disconnect the phone from the network - This switch is generally called the hook switch. It connects when you lift the handset. A speaker - This is generally a little cent, 8-ohm speaker of some sort. A microphone - In the past, telephone microphones have been as simple as carbon granules compressed between two thin metal plates.
Sound waves from your voice compress and decompress the granules, changing the resistance of the granules and modulating the current flowing through the microphone. Telephones: Wires and Cables " ". Telephone wires and cables connect your home phone to a huge communications web. Digital Phone Calls The concentrator digitizes your voice at a sample rate of 8, samples per second and 8-bit resolution see How Analog and Digital Recording Works for information on digitizing sounds.
Hand Generated! Creating Your Own Telephone Network " ". Creating your own telephone network is a rather simple process. Learn about creating your own telephone network or a private intercom. Calling Someone. Read More. Telephones: Tones In a modern phone system, the operator has been replaced by an electronic switch.
Telephones: Bandwidth In order to allow more long-distance calls to be transmitted, the frequencies transmitted are limited to a bandwidth of about 3, hertz.
Compare these two voices: Click here to hear a normal voice. Click here to hear the same voice on the telephone. Telephone FAQ Who invented the telephone? Alexander Graham Bell invented the telephone in , though there's some controversy over whether Bell was the true pioneer.
When did telephones become common in homes? By , roughly 30 percent of houses had a telephone. This rose to about 62 percent in the '50s and 90 percent in the '90s. What are the parts of a telephone? A telephone is made up of a power source, switch hook, dialer, ringer, transmitter, receiver, and an anti-sidetone circuit. Where does the word telephone come from? How do telephones work? A traditional landline telephone system only contains three simple parts: a hook switch, which connects and disconnects the phone from the network; a speaker; and a microphone, through which sound waves from your voice compress and decompress the granules, changing the resistance and modulating the current flowing through the microphone.
How does Caller ID work? Cite This!
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