A telephone, or phone, is a telecommunications device that permits two
or more users to conduct a conversation when they are too far apart to
be 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.
In 1876, Scottish emigrant
Alexander Graham Bell
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. This instrument was
further developed by many others. The telephone was the first device
in history that enabled people to talk directly with each other across
large distances. Telephones rapidly became indispensable to
businesses, government, and households, and are today some of the most
widely used small appliances.
The essential elements of a telephone are a microphone (transmitter)
to speak into and an earphone (receiver) which reproduces the voice in
a distant location. In addition, most telephones contain a ringer
which produces a sound to announce an incoming telephone call, and a
dial or keypad used to enter a telephone number when initiating a call
to another telephone. Until approximately the 1970s most telephones
used a rotary dial, which was superseded by the modern DTMF
push-button dial, first introduced to the public by AT&T in
1963. The receiver and transmitter are usually built into a handset
which is held up to the ear and mouth during conversation. The dial
may be located either on the handset, or on a base unit to which the
handset is connected. The transmitter converts the sound waves to
electrical signals which are sent through a telephone network to the
receiving telephone which converts the signals into audible sound in
the receiver, or sometimes a loudspeaker. Telephones are duplex
devices, meaning they permit transmission in both directions
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. This
gave rise to landline telephone service in which each telephone is
connected by a pair of dedicated wires to a local central office
switching system, which developed into fully automated systems
starting in the early 1900s. For greater mobility, various radio
systems were developed for transmission between mobile stations on
ships and automobiles in the middle 20th century. Hand-held mobile
phones were introduced for personal service starting in 1973. By the
late 1970s several mobile telephone networks operated around the
world. In 1983, the
Advanced Mobile Phone System
Advanced Mobile Phone System (AMPS) was launched,
offering a standardized technology providing portability for users far
beyond the personal residence or office. These analog cellular system
evolved into digital networks with better security, greater capacity,
better regional coverage, and lower cost. Today, the worldwide public
switched telephone network, with its hierarchical system of many
switching centers, can connect any telephone on the network with any
other. With the standardized international numbering system, E.164,
each telephone line has an identifying telephone number, that may be
called from any other, authorized telephone on the network.
Although originally designed for simple voice communications,
convergence has enabled most modern cell phones to have many
additional capabilities. They may be able to record spoken messages,
send and receive text messages, take and display photographs or video,
play music or games, surf the Internet, do road navigation or immerse
the user in virtual reality. Since 1999, the trend for mobile phones
is smartphones that integrate all mobile communication and computing
1 Basic principles
2 Details of operation
3.1 Early development
3.2 Early commercial instruments
4 Digital telephones and voice over IP
8 See also
10 Further reading
11 External links
Schematic of a landline telephone installation.
A traditional landline telephone system, also known as plain old
telephone service (POTS), commonly carries both control and audio
signals on the same twisted pair (C in diagram) of insulated wires,
the telephone line. The control and signaling equipment consists of
three components, the ringer, the hookswitch, and a dial. The ringer,
or beeper, light or other device (A7), alerts the user to incoming
calls. The hookswitch signals to the central office that the user has
picked up the handset to either answer a call or initiate a call. A
dial, if present, is used by the subscriber to transmit a telephone
number to the central office when initiating a call. Until the 1960s
dials used almost exclusively the rotary technology, which was
replaced by dual-tone multi-frequency signaling (DTMF) with pushbutton
A major expense of wire-line telephone service is the outside wire
plant. Telephones transmit both the incoming and outgoing speech
signals on a single pair of wires. A twisted pair line rejects
electromagnetic interference (EMI) and crosstalk better than a single
wire or an untwisted pair. The strong outgoing speech signal from the
microphone (transmitter) does not overpower the weaker incoming
speaker (receiver) signal with sidetone because a hybrid coil (A3) and
other components compensate the imbalance. The junction box (B)
arrests lightning (B2) and adjusts the line's resistance (B1) to
maximize the signal power for the line length. Telephones have similar
adjustments for inside line lengths (A8). The line voltages are
negative compared to earth, to reduce galvanic corrosion. Negative
voltage attracts positive metal ions toward the wires.
Details of operation
The landline telephone contains a switchhook (A4) and an alerting
device, usually a ringer (A7), that remains connected to the phone
line whenever the phone is "on hook" (i.e. the switch (A4) is open),
and other components which are connected when the phone is "off hook".
The off-hook components include a transmitter (microphone, A2), a
receiver (speaker, A1), and other circuits for dialing, filtering
(A3), and amplification.
A calling party wishing to speak to another party will pick up the
telephone's handset, thereby operating a lever which closes the
switchhook (A4), which powers the telephone by connecting the
transmitter (microphone), receiver (speaker), and related audio
components to the line. The off-hook circuitry has a low resistance
(less than 300 ohms) which causes a direct current (DC), which comes
down the line (C) from the telephone exchange. The exchange detects
this current, attaches a digit receiver circuit to the line, and sends
a dial tone to indicate readiness. On a modern push-button telephone,
the caller then presses the number keys to send the telephone number
of the called party. The keys control a tone generator circuit (not
shown) that makes
DTMF tones that the exchange receives. A rotary-dial
telephone uses pulse dialing, sending electrical pulses, that the
exchange can count to get the telephone number (as of 2010 many
exchanges were still equipped to handle pulse dialing). If the called
party's line is available, the exchange sends an intermittent ringing
signal (about 75 volts alternating current (AC) in North America and
UK and 60 volts in Germany) to alert the called party to an incoming
call. If the called party's line is in use, the exchange returns a
busy signal to the calling party. However, if the called party's line
is in use but has call waiting installed, the exchange sends an
intermittent audible tone to the called party to indicate an incoming
The ringer of a telephone (A7) is connected to the line through a
capacitor (A6), which blocks direct current but passes the alternating
current of the ringing signal. The telephone draws no current when it
is on hook, while a DC voltage is continually applied to the line.
Exchange circuitry (D2) can send an AC current down the line to
activate the ringer and announce an incoming call. When there is no
automatic exchange, telephones have hand-cranked magnetos to generate
a ringing voltage back to the exchange or any other telephone on the
same line. When a landline telephone is inactive (on hook), the
circuitry at the telephone exchange detects the absence of direct
current to indicate that the line is not in use. When a party
initiates a call to this line, the exchange sends the ringing signal.
When the called party picks up the handset, they actuate a
double-circuit switchhook (not shown) which may simultaneously
disconnects the alerting device and connects the audio circuitry to
the line. This, in turn, draws direct current through the line,
confirming that the called phone is now active. The exchange circuitry
turns off the ring signal, and both telephones are now active and
connected through the exchange. The parties may now converse as long
as both phones remain off hook. When a party hangs up, placing the
handset back on the cradle or hook, direct current ceases in that
line, signaling the exchange to disconnect the call.
Calls to parties beyond the local exchange are carried over trunk
lines which establish connections between exchanges. In modern
telephone networks, fiber-optic cable and digital technology are often
employed in such connections. Satellite technology may be used for
communication over very long distances.
In most landline telephones, the transmitter and receiver (microphone
and speaker) are located in the handset, although in a speakerphone
these components may be located in the base or in a separate
enclosure. Powered by the line, the microphone (A2) produces a
modulated electric current which varies its frequency and amplitude in
response to the sound waves arriving at its diaphragm. The resulting
current is transmitted along the telephone line to the local exchange
then on to the other phone (via the local exchange or via a larger
network), where it passes through the coil of the receiver (A3). The
varying current in the coil produces a corresponding movement of the
receiver's diaphragm, reproducing the original sound waves present at
Along with the microphone and speaker, additional circuitry is
incorporated to prevent the incoming speaker signal and the outgoing
microphone signal from interfering with each other. This is
accomplished through a hybrid coil (A3). The incoming audio signal
passes through a resistor (A8) and the primary winding of the coil
(A3) which passes it to the speaker (A1). Since the current path A8
– A3 has a far lower impedance than the microphone (A2), virtually
all of the incoming signal passes through it and bypasses the
At the same time the DC voltage across the line causes a DC current
which is split between the resistor-coil (A8-A3) branch and the
microphone-coil (A2-A3) branch. The DC current through the
resistor-coil branch has no effect on the incoming audio signal. But
the DC current passing through the microphone is turned into AC
current (in response to voice sounds) which then passes through only
the upper branch of the coil's (A3) primary winding, which has far
fewer turns than the lower primary winding. This causes a small
portion of the microphone output to be fed back to the speaker, while
the rest of the AC current goes out through the phone line.
A lineman's handset is a telephone designed for testing the telephone
network, and may be attached directly to aerial lines and other
History of the telephone
History of the telephone and Timeline of the telephone
Invention of the telephone,
Elisha Gray and
Alexander Bell telephone controversy, and Canadian Parliamentary
Motion on Alexander Graham Bell
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 called it "telephone". A communication device for
sailing vessels The
Telephone was the invention of a captain John
Taylor in 1844. This instrument used four air horns to communicate
with vessels in foggy weather. Later, c. 1860, Johann Philipp Reis
used the term in reference to his Reis telephone, his device appears
to be the first such device based on 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
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.
Alexander Graham Bell
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. The Bell patents were forensically
victorious and commercially decisive. That first patent by Bell was
the master patent of the telephone, from which other patents for
electric telephone devices and features flowed.
In 1876, shortly after the telephone was invented, Hungarian engineer
Tivadar Puskás invented the telephone switch, which allowed for the
formation of telephone exchanges, and eventually networks.
Main article: Timeline of the telephone
Acoustic telephone ad, The Consolidated
Telephone Co., Jersey City, NJ
1896 telephone from Sweden
Wooden wall telephone with a hand-cranked magneto generator
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
Johann Philipp Reis (1834–1874) publicly
Reis telephone before the Physical Society of
Frankfurt. Reis' 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 Mr. Manzetti illustrated his method for
transmitting spoken words on the telegraph wire intend to apply said
invention in England on several private telegraph lines". 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
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 regular 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 a 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
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
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: Edison files for a patent on a carbon (graphite)
transmitter. The patent 474,230 was granted 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 water
microphone, some had a metal diaphragm that induced current in an
electromagnet wound around a permanent magnet, and some were dynamic -
their diaphragm vibrated a coil of wire in the field of a permanent
magnet or the coil vibrated the diaphragm. The sound-powered dynamic
variants survived in small numbers through the 20th century in
military and maritime applications, where its ability to create its
own electrical power was crucial. Most, however, used the
Edison/Berliner 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
ground return used to complete the circuit (as used in 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
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
New York City
New York City and San Francisco, and Bell was not slow in
appreciating the potential.
Signalling began in an appropriately primitive manner. The user
alerted the other end, or the exchange operator, by whistling into the
transmitter. Exchange operation soon resulted in telephones being
equipped with a bell in a ringer box, first operated over a second
wire, and later over the same wire, but with a condenser (capacitor)
in series with the bell coil to allow the AC ringer signal through
while still blocking DC (keeping the phone "on hook"). Telephones
connected to the earliest
Strowger switch automatic exchanges had
seven wires, one for the 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
Rural and other telephones that were not on a common battery exchange
had a magneto hand-cranked generator to produce a high voltage
alternating signal to ring the bells of other telephones on the line
and to alert the operator. Some local farming communities that were
not connected to the main networks set up barbed wire telephone lines
that exploited the existing system of field fences to transmit the
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". 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 hum from
nearby AC power wires had already led to the use of twisted pairs and,
for long distance telephones, four-wire circuits. Users at the
beginning of the 20th century did not place long distance calls from
their own telephones but made an appointment to use a special
soundproofed long distance telephone booth furnished with the latest
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 sat 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 induction 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. 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 1 to 10 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
rotary dial becoming commonplace in the 1930s in many areas enabled
customer-dialed service, but some magneto systems remained even into
the 1960s. After World War II, the telephone networks saw rapid
expansion and more efficient telephone sets, such as the model 500
telephone in the United States, were developed that permitted larger
local networks centered around central offices. A breakthrough new
technology was the introduction of Touch-Tone signaling using
push-button telephones by American
(AT&T) in 1963.
Ericsson DBH 1001 (ca. 1931), the first combined telephone made with a
Bakelite housing and handset.
Telephone used by American soldiers (WWII, Minalin, Pampanga,
Video shows the operation of an Ericofon
AT&T push button telephone made by Western Electric model 2500 DMG
A candlestick phone
Modern sound-powered emergency telephone
A mobile phone, also called a cell phone
Digital telephones and voice over IP
An IP desktop telephone attached to a computer network, with
Fixed telephone lines per 100 inhabitants 1997–2007
The invention of the transistor in 1947 dramatically changed the
technology used in telephone systems and in the long-distance
transmission networks. With the development of electronic switching
systems in the 1960s, telephony gradually evolved towards digital
telephony which improved the capacity, quality, and cost of the
The development of digital data communications method, such as the
protocols used for the Internet, it became possible to digitize voice
and transmit it as real-time data across computer networks, giving
rise to the field of
Internet Protocol (IP) telephony, also known as
Internet Protocol (VoIP), a term that reflects the
methodology memorably. VoIP has proven to be a disruptive technology
that is rapidly replacing traditional telephone network
As of January 2005, up to 10% of telephone subscribers in
South Korea have switched to this digital telephone service. A January
Newsweek article suggested that
Internet telephony may be "the
next big thing." As of 2006 many VoIP companies offer service to
consumers and businesses.
From a customer perspective, IP telephony uses a high-bandwidth
Internet connection and specialized customer premises equipment to
transmit telephone calls via the Internet, or any modern private data
network. The customer equipment may be an analog telephone adapter
(ATA) which interfaces a conventional analog telephone to the IP
networking equipment, or it may be an
IP Phone that has the networking
and interface technology built into the desk-top set and provides the
traditional, familiar parts of a telephone, the handset, the dial or
keypad, and a ringer in a package that usually resembles a standard
In addition, many computer software vendors and telephony operators
provide softphone application software that emulates a telephone by
use of an attached microphone and audio headset, or loud speaker.
Despite the new features and conveniences of IP telephones, some may
have notable disadvantages compared to traditional telephones. Unless
the IP telephone's components are backed up with an uninterruptible
power supply or other emergency power source, the phone ceases to
function during a power outage as can occur during an emergency or
disaster when the phone is most needed. Traditional phones connected
to the older
PSTN network do not experience that problem since they
are powered by the telephone company's battery supply, which will
continue to function even if there is a prolonged power outage.
Another problem in Internet-based services is the lack of a fixed
physical location, impacting the provisioning of emergency services
such as police, fire or ambulance, should someone call for them.
Unless the registered user updates the IP phone's physical address
location after moving to a new residence, emergency services can be,
and have been, dispatched to the wrong location.
Graphic symbols used to designate telephone service or phone-related
information in print, signage, and other media include ℡ (U+2121),
☎ (U+260E), ☏ (U+260F), ✆ (U+2706), and ⌕ (U+2315).
In 2002, only 10% of the world’s population used cell phones and by
2005 that percentage had risen to 46%.  By the end of 2009, there
were a total of nearly 6 billion mobile and fixed-line telephone
subscribers worldwide. This included 1.26 billion fixed-line
subscribers and 4.6 billion mobile subscribers.
"US 174,465". pdfpiw.uspto.gov. —
Telegraphy (Bell's first
telephone patent)—Alexander Graham Bell
Telegraphy (permanent magnet
receiver)—Alexander Graham Bell
Telegraph (graphite transmitter)—Thomas Edison
Telephone (carbon button transmitter)—Thomas
Telephone (carbon granules transmitter)—Thomas
Telephone (solid back carbon transmitter)—Anthony C.
White (Bell engineer) This design was used until 1925 and installed
phones were used until the 1940s.
US 3,449,750—Duplex Radio Communication and Signalling Appartus—G.
US 3,663,762—Cellular Mobile Communication System—Amos Edward Joel
Telephone System (DynaTAC cell phone)—Martin
Cooper et al. (Motorola)
Index of telephone-related articles
List of telephone operating companies
Tip and ring
^ Dodd, Annabel Z., The Essential Guide to Telecommunications.
Prentice Hall PTR, 2002, p. 183.
^ a b c Kempe, Harry Robert; Garcke, Emile (1911). "Telephone".
In Chisholm, Hugh. Encyclopædia Britannica. 26 (11th ed.). Cambridge
University Press. pp. 547–557.
^ Timbs, John; "Year Book of Facts in Science and Art", 1844 edition,
p. 55. Google Books. This citation is referred to also in the book
Telephone Exchanges" by J. E. Kingsbury published
^ Coe, Lewis (1995). The
Telephone and It's Several Inventors: A
History. Jefferson, NC: McFarland & Company, Inc. p. 5.
^ Brown, Travis (1994). Historical first patents: the first United
States patent for many everyday things (illustrated ed.). University
of Michigan: Scarecrow Press. p. 179.
^ US 174465 Alexander Graham Bell: "Improvement in Telegraphy"
filed on February 14, 1876, granted on March 7, 1876.
^ "Puskás, Tivadar". Omikk.bme.hu. Retrieved 2010-05-23.
^ "Ringer Boxes". Telephonymuseum.com. Archived from the original on
2001-10-12. Retrieved 2010-05-23.
^ Circuit Diagram, Model 102, Porticus
^ Sheridan, Barrett. "
Newsweek – National News, World News, Health,
Technology, Entertainment and more... - Newsweek.com". MSNBC. Archived
from the original on January 18, 2005. Retrieved 2010-05-23.
^ Next-Generation Networks Set to Transform Communications,
International Telecommunications Union website, 4 September 2007.
Retrieved 5 July 2009.
Brooks, John (1976). Telephone: The first hundred years.
Bruce, Robert V. (1990). Bell:
Alexander Graham Bell
Alexander Graham Bell and the Conquest
of Solitude. Cornell University Press.
Casson, Herbert Newton. (1910) The history of the telephone online.
Coe, Lewis (1995). The
Telephone and Its Several Inventors: A History.
Jefferson, NC: McFarland & Co.
Evenson, A. Edward (2000). The
Patent Conspiracy of 1876:
Elisha Gray – Alexander Bell Controversy. Jefferson, NC:
McFarland & Co.
Fischer, Claude S. (1994) America calling: A social history of the
telephone to 1940 (Univ of California Press, 1994)
Huurdeman, Anton A. (2003). The Worldwide History of
Telecommunications Hoboken: NJ: Wiley-IEEE Press.
John, Richard R. (2010). Network Nation: Inventing American
Telecommunications. Cambridge, MA: Harvard University Press.
MacDougall, Robert. The People's Network: The Political Economy of the
Telephone in the Gilded Age. Philadelphia: University of Pennsylvania
Mueller, Milton. (1993) "Universal service in telephone history: A
reconstruction." Telecommunications Policy 17.5 (1993): 352-369.
Todd, Kenneth P. (1998), A Capsule History of the Bell System.
Telegraph Company (AT&T).
Wikimedia Commons has media related to Telephone.
Wikivoyage has a travel guide for
Telephone service for travel.
Look up telephone or cordless telephone in Wiktionary, the free
Telephone Industry Data
"Telephone". New International Encyclopedia. 1905.
Kempe, Harry Robert; Garcke, Emile (1911). "Telephone".
Encyclopædia Britannica. 26 (11th ed.). pp. 547–557.
Virtual museum of early telephones
The Telephone, 1877
The short film "Now You're Talking (1927)" is available for free
download at the
The short film "Communication (1928)" is available for free download
The short film "
Telephone Memories (Reel 1 of 2) (1931)" is available
for free download at the
The short film "
Telephone Memories (Reel 2 of 2) (1931)" is available
for free download at the
The short film "Far Speaking (ca. 1935)" is available for free
download at the
Cable protection system
Prepay mobile phone
Timeline of communication technology
Undersea telegraph line
Edwin Howard Armstrong
John Logie Baird
Alexander Graham Bell
Jagadish Chandra Bose
Lee de Forest
Erna Schneider Hoover
Charles K. Kao
Alexander Stepanovich Popov
Johann Philipp Reis
Vladimir K. Zworykin
Free-space optical communication
Network switching (circuit
Public Switched Telephone
World Wide Web