History of the Telephone
What is a Telephone?
The telephone is a telecommunications device that transmits and receives sound, most commonly the human voice. Telephones are a point-to-point communication system whose most basic function is to allow two people separated by large distances to talk to one another. It is one of the most common household appliances in the developed world, and has long been considered indispensable to business, industry and government.
Who Invented the Telephone?
Credit for the invention of the electric telephone is frequently disputed, and new controversies over the issue have arisen from time-to-time. As with other great inventions such as radio, television, light bulb, and computer, there were several inventors who did pioneering experimental work on voice transmission over a wire and improved on each other’s ideas. Innocenzo Manzetti, Antonio Meucci, Johann Philipp Reis, Elisha Gray, Alexander Graham Bell, and Thomas Edison, among others, have all been credited with pioneering work on the telephone.
Who was first awarded the patent for the Telephone?
An undisputed fact is that Alexander Graham Bell was the first to be awarded a patent for the electric telephone by the United States Patent and Trademark Office in March 1876. That first patent by Bell was the master patent of the telephone, from which all other patents for electric telephone devices and features flowed.
Who invented the telephone switchboard?
A Hungarian engineer, Tivadar Puskás quickly invented the telephone switchboard in 1876, which allowed for the formation of telephone exchanges, and eventually networks.
How does a telephone work?
A traditional landline telephone system, commonly handles both signaling and audio information on the same pair of wires which we know as the phone chord. Although originally designed for voice communication, the system has been adapted for data communication such as Telex, Fax and Internet communication. The signaling equipment consists of a bell, beeper, light or other device to alert the user to incoming calls, and number buttons or a rotary dial to enter a telephone number for outgoing calls. A twisted pair line is preferred as it is more effective at rejecting electromagnetic interference and crosstalk than an untwisted pair.
The telephone consists of an alerting device, usually a ringer, that remains connected to the phone line whenever the phone is “on hook”, and other components which are connected when the phone is “off hook”. These include a microphone, a speaker and other circuits for dialing, filtering, and amplification. A calling party wishing to speak to another party will pick up the telephone’s handset, thus operating a button switch, which puts the telephone into an active state by connecting the mic, speaker and related audio components to the line. This circuitry has a low resistance which causes DC current from the telephone exchange to flow through the line. The exchange detects this DC current, attaches a digit receiver circuit to the line, and sends a dial tone to indicate readiness. On a modern push-button telephone, the calling party then presses the number buttons in a sequence corresponding to the telephone number of the called party. The buttons are connected to a tone generator circuit that produces DTMF tones which end up at a circuit at the exchange. A rotary dial telephone employs pulse dialing, sending electrical pulses corresponding to the telephone number to the exchange. Provided the called party’s line is not already active or “busy”, the exchange sends an intermittent ringing signal to alert the called party to an incoming call. If the called party’s line is active, the exchange sends a busy signal to the calling party. However, if the called party’s line is active but has call waiting installed, the exchange sends an intermittent audible tone to the called party to indicate an incoming call.
The phone’s ringer is connected to the line through a capacitor, a device which blocks the flow of DC current but permits AC current. This constitutes a mechanism whereby the phone draws no current when it is on hook, but exchange circuitry can send an AC voltage down the line to activate the ringer for an incoming call. When a landline phone is inactive or “on hook”, the circuitry at the telephone exchange detects the absence of DC current flow and therefore “knows” that the phone is on hook with only the alerting device electrically connected to the line. When a party initiates a call to this line, and the ringing signal is transmitted. When the called party picks up the handset, they actuate a double-circuit switch which simultaneously disconnects the alerting device and connects the audio circuitry to the line. This, in turn, draws DC current through the line, confirming that the called phone is now active. The exchange circuitry turns off the ring signal, and both phones 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, DC current ceases to flow in that line, signaling the exchange to disconnect the call.
A timeline of the history of the Telephone (1844-1877)
1844: Innocenzo Manzetti first mooted the idea of a “speaking telegraph”.
August 1854: Charles Bourseul publishes an article in a magazine L’Illustration, “Transmission electrique de la parole”.
October 1861: Johann Philipp Reis publicly demonstrated the Reis telephone before the Physical Society of Frankfurt
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.”
December 1871: Antonio Meucci files a patent caveat in the U.S. Patent Office titled “Sound Telegraph”, describing communication of voice between two people by wire.
1874: Meucci, after having renewed the caveat for two years, fails to find the money to renew it. The caveat lapses.
April 1875: Bell’s U.S. Patent 161,739 “Transmitters and Receivers for Electric Telegraphs” using multiple vibrating steel reeds in make-break circuits.
February 1876: Gray invents a liquid transmitter for use with a telephone but does not build one.
February 1876: Elisha Gray files a patent caveat for transmitting the human voice through a telegraphic circuit.
February 1876: Alexander Bell applies for the patent “Improvements in Telegraphy”, for electromagnetic telephones using undulating currents.
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.
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.
March 1876: The first successful telephone transmission of clear speech using a liquid transmitter.
January 1877: Bell’s U.S. patent 186,787 is granted for an electromagnetic telephone using permanent magnets, iron diaphragms, and a call bell.
April 1877: Edison files for a patent on a carbon transmitter. The patent 474,230 was granted 3 May 1892, after a 15 year delay because of litigation.
Telephone Patents Numbers
US 174,465: Telegraphy: Alexander Graham Bell
US 186,787: Electric Telegraphy (permanent magnet receiver): Alexander Graham Bell
US 474,230: Speaking Telegraph (graphite transmitter): Thomas Edison
US 203,016: Speaking Telephone (carbon button transmitter): Thomas Edison
US 222,390: Carbon Telephone (carbon granules transmitter): Thomas Edison
US 485,311: Telephone (solid back carbon transmitter): Anthony C. White
US 3,449,750: Duplex Radio Communication and Signalling Appartus: G. H. Sweigert
US 3,663,762: Cellular Mobile Communication System: Amos Edward Joel (Bell Labs)
US 3,906,166: Radio Telephone System (DynaTAC cell phone): Martin Cooper et al. (Motorola)
How were early telephones used?
Early telephones were technically diverse. Some used a liquid transmitter, 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 dynamic kind 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, actually acting as an impedance matching transformer to make it compatible to 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, “common battery” operation came to dominate, powered by “talk battery” from the telephone exchange over the same wires that carried the voice signals.
Early telephones used a single wire for the subscriber’s line, with ground return used to complete the circuit. The earliest dynamic telephones also had only one port opening for sound, with the user alternately listening and speaking into the same hole. Sometimes the instruments were operated in pairs at each end, making conversation more convenient but also more expensive.
What is a digital telephone?
The Public Switched Telephone Network has gradually evolved towards digital telephony which has improved the capacity and quality of the network. End-to-end analog telephone networks were first modified in the early 1960s by upgrading transmission networks with T1 carrier systems, designed to support the basic 3 kHZ voice channel by sampling the bandwidth-limited analog voice signal and encoding using PCM. While digitization allows wideband voice on the same channel, the improved quality of a wider analog voice channel did not find a large market in the PSTN.
What is VOIP?
Internet Protocol telephony, is a disruptive technology that is rapidly gaining ground against traditional telephone network technologies. As of January 2005, up to 10% of telephone subscribers in Japan and South Korea have switched to this digital telephone service.