Telephone

Page semi-protected
Source: Wikipedia, the free encyclopedia.

AT&T push button telephone made by Western Electric, model 2500 DMG black, 1980
Telephone
InventorAlexander Graham Bell
Inception1876; 148 years ago (1876)

A telephone is a

mobile phones, due to technological convergence
.

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.[2] 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

electrical signals which are sent through the telecommunication system to the receiving telephone, which converts the signals into audible sound in the receiver or sometimes a loudspeaker
. 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 telecommunication system, but other methods existed in the early history of the telephone.

The first telephones were directly connected to each other from one customer's office or residence to another customer's location. Being impractical beyond just a few customers, these systems were quickly replaced by manually operated centrally located switchboards. These exchanges were soon connected together, eventually forming an automated, worldwide public switched telephone network (PSTN). For greater mobility, various radio systems were developed for transmission between mobile stations on ships and automobiles in the mid-20th century. Hand-held mobile phones were introduced for personal service starting in 1973. In later decades, their analog cellular system evolved into digital networks with greater capability and lower cost.

Early history

Alexander Graham Bell's Telephone Patent Drawing
Replica of the telettrofono, invented by Antonio Meucci and credited by several sources as the first telephone[4]
Bell placing the first New York to Chicago telephone call in 1892

Before the development of the electric telephone, the term telephone was applied to other inventions, and not all early researchers of the electrical device used the term. Perhaps the earliest use of the word for a communications system was the telephon created by Johann Sigismund Gottfried Huth in 1796. Huth proposed an alternative to the optical telegraph of Claude Chappe in which the operators in the signaling towers would shout to each other by means of what he called "speaking tubes", but would now be called giant megaphones.[5] A communication device for sailing vessels, called telephone, was invented by Captain John Taylor in 1844. This instrument used four air horns to communicate with vessels in foggy weather.[6][7]

Johann Philipp Reis used the term in reference to his invention, commonly known as the Reis telephone, in c. 1860. His device appears to be the first device based on the conversion of sound into electrical impulses.

The term telephone was adopted into the vocabulary of many languages. It is derived from the Greek: τῆλε, tēle, "far" and φωνή, phōnē, "voice", together meaning "distant voice".

Credit for the invention of the electric telephone is frequently disputed. As with other influential inventions such as radio, television, the light bulb, and the computer, several inventors pioneered experimental work on voice transmission over a wire and improved on each other's ideas. New controversies over the issue still arise from time to time. Charles Bourseul, Antonio Meucci, Johann Philipp Reis, Alexander Graham Bell, and Elisha Gray, amongst others, have all been credited with the invention of the telephone.[8][9]

Alexander Graham Bell was the first to be awarded a patent for the electric telephone by the United States Patent and Trademark Office (USPTO) in March 1876.[10] Before Bell's patent, the telephone transmitted sound in a way that was similar to the telegraph. This method used vibrations and circuits to send electrical pulses, but was missing key features. Bell found that this method produced a sound through intermittent currents, but in order for the telephone to work a fluctuating current reproduced sounds the best. The fluctuating currents became the basis for the working telephone, creating Bell's patent.[11] That first patent by Bell was the master patent of the telephone, from which other patents for electric telephone devices and features flowed.[12]

In 1876, shortly after Bell's patent application, Hungarian engineer Tivadar Puskás proposed the telephone switch, which allowed for the formation of telephone exchanges, and eventually networks.[13]

In the United Kingdom, the blower is used as a slang term for a telephone. The term came from navy slang for a speaking tube.[14] In the U.S., a somewhat dated slang term refers to the telephone as "the horn", as in "I couldn't get him on the horn", or "I'll be off the horn in a moment."[15]

Timeline of early development

Reis's telephone, the first device to transmit a voice via electronic signals and for that the first modern telephone.[16][17] Reis also coined the term.[18]
Bell's first telephone transmitter, c. 1876, reenacted 50 years later
Acoustic telephone ad, The Consolidated Telephone Co., Jersey City, New Jersey, 1886
1896 telephone from Sweden
Wooden wall telephone with a hand-cranked magneto generator
  • 1844: Innocenzo Manzetti first mooted the idea of a "speaking telegraph" or telephone. Use of the "speaking telegraph" and "sound telegraph" monikers would eventually be replaced by the newer, distinct name, "telephone".
  • 26 August 1854: Charles Bourseul published an article in the magazine L'Illustration (Paris): "Transmission électrique de la parole" (electric transmission of speech), describing a "make-and-break" type telephone transmitter later created by Johann Reis.
  • 26 October 1861: Johann Philipp Reis (1834–1874) publicly demonstrated the Reis telephone before the Physical Society of Frankfurt.[9] Reis's telephone was not limited to musical sounds. Reis also used his telephone to transmit the phrase "Das Pferd frisst keinen Gurkensalat" ("The horse does not eat cucumber salad").
  • 22 August 1865, La Feuille d'Aoste reported "It is rumored that English technicians to whom Manzetti illustrated his method for transmitting spoken words on the telegraph wire intend to apply said invention in England on several private telegraph lines".[citation needed] However, telephones would not be demonstrated there until 1876, with a set of telephones from Bell.
  • 28 December 1871: Antonio Meucci files patent caveat No. 3335 in the U.S. Patent Office, titled "Sound Telegraph", describing communication of voice between two people by wire. A patent caveat was not an invention patent award, but only an unverified notice filed by an individual that he or she intends to file a patent application in the future.
  • 1874: Meucci, after having renewed the caveat for two years does not renew it again, and the caveat lapses.
  • 6 April 1875: Bell's U.S. Patent 161,739 "Transmitters and Receivers for Electric Telegraphs" is granted. This uses multiple vibrating steel reeds in make-break circuits.
  • 11 February 1876: Elisha Gray invents a liquid transmitter for use with the telephone but does not build one.
  • 14 February 1876: Gray files a patent caveat for transmitting the human voice through a telegraphic circuit.
  • 14 February 1876: Alexander Graham Bell applies for the patent "Improvements in Telegraphy", for electromagnetic telephones using what is now called amplitude modulation (oscillating current and voltage) but which he referred to as "undulating current".
  • 19 February 1876: Gray is notified by the U.S. Patent Office of an interference between his caveat and Bell's patent application. Gray decides to abandon his caveat.
  • 7 March 1876: Bell's U.S. patent 174,465 "Improvement in Telegraphy" is granted, covering "the method of, and apparatus for, transmitting vocal or other sounds telegraphically…by causing electrical undulations, similar in form to the vibrations of the air accompanying the said vocal or other sound."
  • 10 March 1876: The first successful telephone transmission of clear speech using a liquid transmitter when Bell spoke into his device, "Mr. Watson, come here, I want to see you." and Watson heard each word distinctly.
  • 30 January 1877: Bell's U.S. patent 186,787 is granted for an electromagnetic telephone using permanent magnets, iron diaphragms, and a call bell.
  • 27 April 1877: Thomas Edison files a patent application for a carbon (graphite) transmitter. It was published as No. 474,230 on 3 May 1892, after a 15-year delay because of litigation. Edison was granted patent 222,390 for a carbon granules transmitter in 1879.

Early commercial instruments

Early telephones were technically diverse. Some used a

carbon transmitter, which was much louder than the other kinds, even though it required an induction coil which was an impedance matching
transformer to make it compatible with the impedance of the line. The Edison patents kept the Bell monopoly viable into the 20th century, by which time the network was more important than the instrument.

Early telephones were locally powered, using either a dynamic transmitter or by the powering of a transmitter with a local battery. One of the jobs of outside plant personnel was to visit each telephone periodically to inspect the battery. During the 20th century, telephones powered from the telephone exchange over the same wires that carried the voice signals became common.

Early telephones used a single wire for the subscriber's line, with

telegraphs
). The earliest dynamic telephones also had only one port opening for sound, with the user alternately listening and speaking (or rather, shouting) into the same hole. Sometimes the instruments were operated in pairs at each end, making conversation more convenient but also more expensive.

At first, the benefits of a telephone exchange were not exploited. Instead, telephones were leased in pairs to a

subscriber, who had to arrange for a telegraph contractor to construct a line between them, for example, between a home and a shop. Users who wanted the ability to speak to several different locations would need to obtain and set up three or four pairs of telephones. Western Union, already using telegraph exchanges, quickly extended the principle to its telephones in New York City and San Francisco
, and Bell was not slow in appreciating the potential.

knife switch, one for each telegraph key, one for the bell, one for the push-button and two for speaking. Large wall telephones in the early 20th century usually incorporated the bell, and separate bell boxes
for desk phones dwindled away in the middle of the century.

Rural and other telephones that were not on a common battery exchange had a

barbed wire telephone lines
that exploited the existing system of field fences to transmit the signal.

In the 1890s a new smaller style of telephone was introduced, packaged in three parts. The transmitter stood on a stand, known as a "candlestick" for its shape. When not in use, the receiver hung on a hook with a switch in it, known as a "switchhook". Previous telephones required the user to operate a separate switch to connect either the voice or the bell. With the new kind, the user was less likely to leave the phone "off the hook". In phones connected to magneto exchanges, the bell, induction coil, battery and magneto were in a separate bell box or "ringer box".[19] In phones connected to common battery exchanges, the ringer box was installed under a desk, or other out-of-the-way place, since it did not need a battery or magneto.

Cradle designs were also used at this time, having a handle with the receiver and transmitter attached, now called a handset, separate from the cradle base that housed the magneto crank and other parts. They were larger than the "candlestick" and more popular.

Disadvantages of single-wire operation such as crosstalk and

long-distance calls from their own telephones but made an appointment and were connected with the assistance of a telephone operator.[20]

What turned out to be the most popular and longest-lasting physical style of telephone was introduced in the early 20th century, including Bell's

202-type desk set. A carbon granule transmitter and electromagnetic receiver were united in a single molded plastic handle, which when not in use was secured in a cradle in the base unit. The circuit diagram of the model 202 shows the direct connection of the transmitter to the line, while the receiver was inductively coupled. In local battery configurations, when the local loop was too long to provide sufficient current from the exchange, the transmitter was powered by a local battery and inductively coupled, while the receiver was included in the local loop.[21]
The coupling transformer and the ringer were mounted in a separate enclosure, called the subscriber set. The dial switch in the base interrupted the line current by repeatedly but very briefly disconnecting the line one to ten times for each digit, and the hook switch (in the center of the circuit diagram) disconnected the line and the transmitter battery while the handset was on the cradle.

In the 1930s, telephone sets were developed that combined the bell and induction coil with the desk set, obviating a separate ringer box. The

Digital telephones and voice over IP

An IP desktop telephone attached to a computer network

The invention of the

digital telephony, which improved the capacity, quality, and cost of the network.[23]

Integrated Services Digital Network (ISDN) was launched in the 1980s, providing businesses and consumers with access to digital telephony services such as data, voice, video, and fax services.[24]

The development of digital data communications methods made it possible to digitize voice and transmit it as real-time data across

disruptive technology that is rapidly replacing traditional telephone network infrastructure.[25]

Fixed telephone lines per 100 inhabitants 1997–2007

By January 2005, up to 10% of telephone subscribers in Japan and South Korea had switched to this digital telephone service. A January 2005 Newsweek article suggested that Internet telephony may be "the next big thing."[26] The technology has spawned a new industry comprising many VoIP companies that offer services to consumers and businesses. The reported global VoIP market in October 2021 was $85.2 billion with a projection of $102.5 billion by 2026.[27]

IP telephony uses high-bandwidth Internet connections and specialized customer premises equipment to transmit telephone calls via the Internet, or any modern private data network. The customer equipment may be an

IP Phone, a dedicated standalone device; or a computer softphone application, utilizing the microphone and headset devices of a personal computer or smartphone.[28]

While traditional analog telephones are typically powered from the central office through the telephone line, digital telephones require a local power supply.[29] Internet-based digital service also requires special provisions to provide the service location to the emergency services when an emergency telephone number is called.[30]

Cordless telephones

A cordless telephone system consisting of a handset resting on a base station (left) and a second handset resting on a battery charger unit (right)

A cordless telephone or portable telephone consists of a base station unit and one or more portable cordless handsets. The base station connects to a telephone line, or provides service by voice over IP (VOIP). The handset communicates with the base station via radio frequency signals. A handset's operational range is limited, usually to within the same building or within a short distance from the base station.

Base station

Base stations include a radio transceiver which enables full-duplex, outgoing and incoming signals and speech with the handsets. The base station often includes a microphone,

audio amplifier, and a loudspeaker to enable hands-free speakerphone conversations, without needing to use a handset. The base station may also have a numeric keypad for dialing, and a display for caller ID. In addition, answering machine function may be built in.[31]

The cordless handset contains a rechargeable battery, which the base station recharges when the handset rests in its cradle. Muilt-handset systems generally also have additional charging stands. A cordless telephone typically requires a constant electricity supply to power the base station and charger units by means of a DC transformer which plugs into a wall AC power outlet.[31]

Mobile phones