Telephone

A telephone, commonly shortened to phone, is a telecommunications device that enables two or more users to conduct a conversation when they are too far apart to be easily heard directly. A telephone converts sound, typically and most efficiently the human voice, into electronic signals that are transmitted via cables and other communication channels to another telephone which reproduces the sound to the receiving user. The term is derived from Ancient Greek: τῆλε, romanized: tēle, lit. 'far' and φωνή (phōnē, voice), together meaning distant voice.

In 1876, Alexander Graham Bell was the first to be granted a United States patent for a device that produced clearly intelligible replication of the human voice at a second device. This instrument was further developed by many others, and became rapidly indispensable in business, government, and in households.

The essential elements of a telephone are a microphone (transmitter) to speak into and an earphone (receiver) which reproduces the voice at a distant location. The receiver and transmitter are usually built into a handset which is held up to the ear and mouth during conversation. Telephones permit transmission in both directions simultaneously.

Most telephones also contain an alerting feature, such as a ringer or a visual indicator, to announce an incoming telephone call. Telephone calls are initiated most commonly with a keypad or dial, affixed to the telephone, to enter a telephone number, which is the address of the call recipient's telephone in the telecommunications system, but other methods existed in the early history 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 communication devices. One early version was created by Gottfried Huth in 1796, who suggested using “speaking tubes” — large megaphones — to shout between signaling towers. In 1844, Captain John Taylor invented a device called a “telephone” for ships, using air horns to communicate in foggy weather.

The term “telephone” became widely used after Johann Philipp Reis created a device around 1860 that could change sound into electrical signals. This was an important step toward the modern telephone. Many inventors, including Alexander Graham Bell and Elisha Gray, worked on early telephones. Bell was the first to receive a patent for an electric telephone in 1876, which helped make the telephone a practical device for everyday use.

Early commercial instruments

Early telephones were different from each other. Some used a water microphone, while others used parts that created electrical current. Most used a special carbon transmitter that made sounds louder. These early phones needed batteries or special power supplies to work.

Phones were originally powered by local batteries, but later ones got power from the telephone exchange. At first, phones used a single wire and shared one opening for both speaking and listening. Later, phones were connected in pairs between two places, like a home and a shop. As telephone exchanges became more common, phones could connect to many different locations. Early phones used simple signals like whistling to get attention, and later added bells to alert users. Over time, phones evolved from large wall models to smaller desk sets and finally to the popular designs we recognize 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 kind of phone that lets people talk to each other using only the energy from their own voices. Instead of needing electricity from batteries or plugs, these phones 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 type of phone that includes a base station and one or more portable handsets. The handset talks to the base station using radio frequency signals. Usually, you can use the handset only within 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 handheld device that lets people talk to each other using radio waves. These phones connect to a network of towers and buildings that send the messages to other phones. The first mobile networks started in 1979, and since then, they have changed a lot, getting better and adding new features.

Mobile phones usually have a small card called a SIM card that holds information about the user. They also have screens that can show pictures and text, and many can even touch them to use. Over time, mobile phones have added many new things like sending text messages, taking pictures, playing music, and connecting to the internet. Today, most mobile phones are "smartphones," which 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 kind of mobile phone that connects to others through satellites orbiting the Earth, rather than through nearby towers like regular cellphones. This means it can work almost anywhere in the world, as long as there is an open sky to see the satellites. Satellite phones can make voice calling, send text messaging, and access the Internet in places where regular phone services aren’t available.

These phones are useful for people exploring remote areas, working on ships, or traveling where there is no cellular network. They are also reliable during natural disasters or conflicts, when regular communication systems might not work.