The telephone is a telecommunications device that transmits and receives sound generally the human voice. The phone’s basic function is to allow people who are separated by large distances to talk with each other. The telephone is used across the world and is one of the most common appliances in the developed world.

The phone is designed to have a microphone, an ear piece which reproduces the voice, a ringer, and a keypad to enter the numbers. The microphone, earphone, and the keypad are all part of the handset, although the keypad could be in a separate part. The landline phone is connected by wire to the telephone network, while a mobile phone is portable and uses radio to connect to the telephone network. There is also the cordless telephone that connects to its base by radio and can only be used within a limited range of the base station.

By converting the sound waves to electrical signals the microphone is able to send the voices through the network to the other end where the earphone translates the signals back into sound waves. They are a duplex communication medium allowing two people to talk simultaneously. The network is worldwide and consists of telephone lines, fiber optic cables, microwave transmissions, cellular networks, satellites, and switching centers that allow any telephone to communicate with any other phone. Since each telephone line has a specific number, it is as simple as dialing the number of the phone you want to reach.

The credit for the invention of the electric telephone is frequently disputed; however, Alexander Graham Bell was the first to get a patent for the electric telephone in 1876. Others who did experimenting on the design of the phone were Innocenzo Manzetti, Antonio Meucci, Johann Philipp, Elisha Gray, and Thomas Edison. Bell’s patent was the master patent in which all other telephone patents flowed.

Tivadar Puskás created the telephone switchboard in 1876, which allowed for telephone exchanges and networks. The telephone line is made up of a pair of insulated wires. Although it was originally designed for voice the system has been adopted for Telex, Fax, and dial-up internet. The ringer alerts the receiver of a call to an incoming call who then picks up the phone which is then put into active by the switchhook. The switchook connects the transmitter, receiver, and other audio components. Land line calls are carried through “trunk” lines, however, in modern networks the calls are carried through satellites and fiber optic lines.

Early telephones were created with various parts and were diverse. Some used liquid transmitters and some used metal diaphragms to transfer sound. Most phones use Edison/Berliner carbon transmitter, which was much louder than others. Edison kept patenting his inventions and thus kept the Bell monopoly viable into the 20th century.

Originally phones were sold in pairs and a line was built between the two customers to connect them. To have a connection to more than one location a user would need to set up three or four pairs of phones.

The longest lasting and most popular style of phone was the Model 102. In this design a carbon granule transmitter and electromagnetic receiver were united in a single molded plastic handle. After the 1930′s the base was powered through central office batteries instead of local battery. Nothing much else changed until the 1960′s when Touch-Tone dialing was introduced. Digital telephony has slowly taken over the network due to the improved capacity and quality it gave the network.

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