Telephone

A telephone, commonly shortened to phone, is a telecommunications device that lets two or more people talk when they are far apart. A telephone changes sound, especially the human voice, into electronic signals. These signals travel through cables and other paths to another telephone, which turns the signals back into sound for the person on the other end. The word comes from Ancient Greek: τῆλε, romanized: tēle, lit. 'far' and φωνή (phōnē, voice), meaning distant voice.

In 1876, Alexander Graham Bell was the first to get a United States patent for a device that could clearly copy the human voice on another device. This device was improved by many people and became very important in business, government, and households.

The main parts of a telephone are a microphone (transmitter) to speak into and an earphone (receiver) that plays back the voice from far away. The receiver and transmitter are usually in a handset that you hold to your ear and mouth when talking. Telephones allow talking and listening at the same time.

Most telephones also have a way to alert you, like a ringer or a light, when someone is calling. You usually start a call by using a keypad or dial on the telephone to enter a telephone number, which tells the system where to send the call. Other ways to start a call existed in the early days of the telephone.

Early history

Main article: History of the telephone

Further information: Invention of the telephone and Elisha Gray and Alexander Bell telephone controversy

Before the electric telephone was invented, the word “telephone” was used for other ways to send messages. One early version was made by Gottfried Huth in 1796. He used “speaking tubes” to shout between towers. In 1844, Captain John Taylor made a “telephone” for ships using air horns to talk in foggy weather.

The word “telephone” became common after Johann Philipp Reis made a device around 1860. It could change sound into electrical signals. This was a big step to the telephone we know today. Many inventors, like Alexander Graham Bell and Elisha Gray, worked on early telephones. Bell got the first patent for an electric telephone in 1876. This helped make the telephone useful for everyday life.

Early commercial instruments

Early telephones looked different from each other. Some used a water microphone, while others used parts that made electricity. Most used a special carbon transmitter to make sounds louder. These old phones needed batteries or special power to work.

Phones were first powered by local batteries, but later ones got power from the telephone exchange. At first, phones used one wire and had one opening for both talking and listening. Later, phones connected two places, like a home and a shop. As telephone exchanges became more common, phones could connect to many places. Early phones used simple signals like whistling to get attention, and later added bells to alert users. Over time, phones changed from large wall models to smaller desk sets and then to the designs we know today, including the introduction of rotary dial phones and later push-button telephones.

Sound-powered telephones

Main article: Sound-powered telephone

A sound-powered telephone is a special phone that lets people talk to each other using only the energy from their own voices. These phones do not need electricity from batteries or plugs. They use the sound waves from talking to send messages through wires.

These phones are very useful in places where power might go out or could be dangerous, like airports, ships, mines, and factories. They can work over long distances and are safe to use even where there is a risk of fire or explosions.

Digital telephones and voice over IP

Main articles: Digital telephony and Voice over IP

The invention of the transistor in 1947 changed telephone technology. New ways to control and send signals made telephones better and cheaper.

Later, it became possible to send voice as data over the Internet. This is called voice over Internet Protocol (VoIP). Many people now use VoIP for calls. It works on computers, special phones, or mobile networks.

Cordless telephones

Main article: Cordless telephone

A cordless telephone is a phone with a base station and one or more handsets you can carry. The handset talks to the base station using radio frequency signals. You can usually use the handset only inside a building or a short distance from the base station.

The base station connects to regular phone lines or uses internet calls (VOIP). It has parts that let you talk and listen without holding the handset, like a speakerphone. It might also show who is calling thanks to caller ID. The handset runs on a rechargeable battery that charges when you put it back in the base station. The base station needs to be plugged into power to work.

Mobile phones

Main article: Mobile phone

A mobile phone, also called a cellphone, is a small device people hold to talk to each other. It uses radio waves to send messages. These phones connect to special towers and buildings that help send the messages to other phones. The first mobile phone networks began in 1979, and they have improved a lot since then.

Mobile phones usually have a small card called a SIM card. This card holds information about the user. They also have screens that can show pictures and text. Many phones can be touched to use. Over time, mobile phones have added new features like sending text messages, taking pictures, playing music, and connecting to the internet. Today, most mobile phones are "smartphones." These are like tiny computers that can do even more things, like watching videos and using apps.

Satellite phones

Main article: Satellite phone

A satellite phone is a special mobile phone that connects to others through satellites orbiting the Earth. It works almost anywhere in the world, as long as there is an open sky. Satellite phones can make voice calling, send text messaging, and access the Internet where regular phones cannot.

These phones are useful for people in remote areas, on ships, or where there are no regular phone networks. They are also helpful during natural disasters or conflicts when other phones might not work.