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Telephone
ATTtelephone-large.jpg
A 1970's era AT&T "Touch-Tone" telephone
Inventor Alexander Graham Bell
Launch year 1876
Available? Worldwide
.The telephone (from the Greek: τῆλε, tēle, "far" and φωνή, phōnē, "voice") is a telecommunications device that transmits and receives sound, most commonly the human voice.^ You'll have one antenna for the voice transmit channel, one antenna for the set up or control channel, and two antennas to receive.
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.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.^ In time division multiple access we separate calls by time, one after another.
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^ For most of us, let's go through this again, this time from another point of view.
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^ "Most people see the cell as the blue hexagon, being defined by the tower in the center, with the antennae pointing in the directions indicated by the arrows.
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It is one of the most common household appliances in the developed world, and has long been considered indispensable to business, industry and government. The word "telephone" has been adapted to many languages and is widely recognized around the world.
The device operates principally by converting sound waves into electrical signals, and electrical signals into sound waves. .Such signals when conveyed through telephone networks — and often converted to electronic and/or optical signals — enable nearly every telephone user to communicate with nearly every other worldwide.^ A 30 kHz channel for cellular gives you great sound almost automatically, nearly on par with the normal telephone network.
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^ Broad and deep knowledge of digital switching and transmission technology in the public switched telephone network, radio, signal processing, antennas, etc.
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.Graphic symbols used to designate telephone service or phone-related information in print, signage, and other media include (U+2121), (U+260E), (U+260F), and (U+2706).^ (Time division duplexing, as used in cordless telephone schemes: DECT and Personal Handy Phone systems might have a place but this still isn't clear.
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^ Advanced Mobile Phone Service overcomes these problems be using a novel cellular approach.
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^ Your mobile transmits that telephone number, along with a request for service signal, and all the information used to register a call to the cell site.
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Contents

History

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.^ The CDG states that CDMA systems have seven advantages over other cellular radio transmission techniques.
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^ Six sectored sites have been touted as a Great Thing by manufacturers such as Hughes and Motorola who want to sell you more equipment.
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.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.^ His interview on Alexander Graham Bell will air on the History Channel the end of 2006.
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.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 (USPTO) in March 1876.[1] That first patent by Bell was the master patent of the telephone, from which all other patents for electric telephone devices and features flowed.^ One desirable feature of a mobile telephone system is the ability to roam; that is, subscribers must be able to call and be called in cities other than their home areas.
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^ His interview on Alexander Graham Bell will air on the History Channel the end of 2006.
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The early history of the telephone became and still remains a confusing morass of claims and counterclaims, which were not clarified by the huge mass of lawsuits that hoped to resolve the patent claims of many individuals and commercial competitors. The Bell and Edison patents, however, were forensically victorious and commercially decisive.
A Hungarian engineer, Tivadar Puskás quickly invented the telephone switchboard in 1876, which allowed for the formation of telephone exchanges, and eventually networks. [2]

Basic principles

1896 Telephone from Sweden.
.A traditional landline telephone system, also known as "plain old telephone service" (POTS), commonly handles both signaling and audio information on the same twisted pair of insulated wires: the telephone line.^ The FCC intends cellular service to be regulated by competition, with two competing system providers in each large city: a wire-line carrier and a radio common carrier.
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^ AMPS is actually a hybrid system, combining both digital and analog signals.
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^ More recent systems (the MJ system at 150 KHz and the MK system at 450 KHz) [ Improved Mobile Telephone Service or IMTS, ed.
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.Although originally designed for voice communication, the system has been adapted for data communication such as Telex, Fax and Internet communication.^ Although first in each cell's lineup, most radio engineers place priority on the voice channels in a system.
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^ AMPS, the older, analog voice system, not the digital IS-136, uses frequency shift keying to send data.
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^ Rogers Communications unveiled new data plans designed to work with the launch of its much anticipated iPhone - and the pricing plans line up...

.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.^ All incoming and outgoing calls are then routed over this channel.
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^ In addition to channel assignment, other MTSO functions include maintaining a list of busy (that is, off-hook) mobile units and paging mobile units for which incoming calls are intended.
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^ New gadgets can be complicated at the best of times, especially when you have to overcome the complexities of overseas dialing codes and unfamiliar telephone number formats.
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A twisted pair line is preferred as it is more effective at rejecting electromagnetic interference (EMI) 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 transmitter (microphone), a receiver (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 or "switchhook", which puts the telephone into an active (off hook) state by connecting the transmitter (microphone), receiver (speaker) and related audio components to the line.^ In addition to channel assignment, other MTSO functions include maintaining a list of busy (that is, off-hook) mobile units and paging mobile units for which incoming calls are intended.
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^ Voice traffic is digitized and portions of many calls are put into a single bit stream, one sample at a time.
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^ Your phone stops transmitting it once you pick up the handset or otherwise go off hook to answer the ring.
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.This circuitry has a low resistance (less than 300 Ohms) which causes DC current (48 volts, nominal) from the telephone exchange to flow through the line.^ The data rate is 48.6 Kbits/s, less than a 56K modem, with each slot transmitting 324 bits in 6.67 ms. How is this rate determined?
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.The exchange detects this DC current, attaches a digit receiver circuit to the line, and sends a dial tone to indicate readiness.^ To digress briefly, dial tone is not present on AMPS phones, although E.F. Johnson phones produced land line type dial tone within the unit.
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.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.^ Your mobile transmits that telephone number, along with a request for service signal, and all the information used to register a call to the cell site.
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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.^ To illustrate and compare, sending the number 175 in American Morse Code requires 11 pulses, three more than in binary code.
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(Most exchanges are still equipped to handle pulse dialing.) Provided the called party's line is not already active or "busy", the exchange sends an intermittent ringing signal (about 90 volts 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 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.^ Making a call, however, involves far more problems and resources than an incoming call does.
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^ Registration lets the local system know that a phone is active, in a particular area, and that the mobile can now take incoming calls.
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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.^ In addition to channel assignment, other MTSO functions include maintaining a list of busy (that is, off-hook) mobile units and paging mobile units for which incoming calls are intended.
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^ There was no secret that Nokia is coming up with the new fashion phone line-up this summer.

^ Registration lets the local system know that a phone is active, in a particular area, and that the mobile can now take incoming calls.
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.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.^ Imagine dialing your landline phone without taking the receiver of the hook.
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^ It would have to be a phone that can only call certain people.I'm very paranoid so it would make me feel better to know...

^ As we rely more heavily on mobile phones to stay connected, they increasingly know everything about us and have b...

.When a party initiates a call to this line, and the ringing signal is transmitted.^ Your mobile transmits that telephone number, along with a request for service signal, and all the information used to register a call to the cell site.
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.When the called party picks up the handset, they actuate a double-circuit switchhook which simultaneously disconnects the alerting device and connects the audio circuitry to the line.^ If it's a lousy call, they'll hang up.
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^ Your phone stops transmitting it once you pick up the handset or otherwise go off hook to answer the ring.
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^ For the consumer CDMA appeals since a conversation can't be picked up with a scanner like an analog AMPS call.
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.This, in turn, draws DC current through the line, confirming that the called phone is now active.^ Through generous donations and the recycling of used cell phones, Robbie and Brittany have already distributed thousands of calling cards to soldiers around the globe.
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^ When you turn on your phone the mobile switch determines what cell will carry the call and assigns a vacant radio channel within that cell to take the conversation.
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^ Registration lets the local system know that a phone is active, in a particular area, and that the mobile can now take incoming calls.
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.The exchange circuitry turns off the ring signal, and both phones are now active and connected through the exchange.^ Turning on and off the signal source in the above sequence represents the code.
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^ Your phone stops transmitting it once you pick up the handset or otherwise go off hook to answer the ring.
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^ Registration lets the local system know that a phone is active, in a particular area, and that the mobile can now take incoming calls.
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.The parties may now converse as long as both phones remain off hook.^ Both callers now hear each other's conversation.
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^ A phone's MIN may change but the serial number remains the same.
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^ Your phone stops transmitting it once you pick up the handset or otherwise go off hook to answer the ring.
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.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.^ Cleardown or termination means hanging up, going on hook, or terminating a call.
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^ "Once a call is up on a voice channel, all signaling is done on the voice channel via a scheme known as "Blank and Burst".
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^ If it's a lousy call, they'll hang up.
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.Calls to parties beyond the local exchange are carried over "trunk" lines which establish connections between exchanges.^ This allocation is split equally between wire-line and radio common carriers (each is allocated 333 channels).
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^ In many areas, the wire-line carrier will be the local operating company.
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^ One license went automatically to the local telephone companies, in telecom parlance, the local exchange carriers or LECs.
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.In modern telephone networks, fiber-optic cable and digital technology are often employed in such connections.^ Broad and deep knowledge of digital switching and transmission technology in the public switched telephone network, radio, signal processing, antennas, etc.
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Satellite technology may be used for communication over very long distances.
.In most 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.^ These courses have been given to staff of numerous US and foreign manufacturers of both mobile handset, mobile data, and base equipment.
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Powered by the line, the transmitter produces an electric current whose voltage varies 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 a larger network), where it passes through the coil of the receiver.^ One license went automatically to the local telephone companies, in telecom parlance, the local exchange carriers or LECs.
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^ The first point is that cell phones and base stations transmit or communicate with each other on dedicated paired frequencies called channels.
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^ AT&T The NEW AT&T. Find a cell phone, browse cell phone plans and ringtones along with accessories for your needs at AT&T. AWS WIRELESS ACCESSORIES We offer the most up to date wireless phone accessory line.
  • Cellular Phone Directory of Florida 11 September 2009 20:57 UTC florida.uscity.net [Source type: General]

The varying voltage in the coil produces a corresponding movement of the receiver's diaphragm, reproducing the sound waves present at the transmitter.
A Lineman's handset is a telephone designed for testing the telephone network, and may be attached directly to aerial lines and other infrastructure components.

Early development

Early telephone with hand cranked generator.
  • 1844 — Innocenzo Manzetti first mooted the idea of a “speaking telegraph” (telephone).
  • 26 August 1854 — Charles Bourseul publishes an article in a magazine L'Illustration (Paris) : "Transmission électrique de la parole" [electric transmission of speech].
  • 26 October 1861 — Johann Philipp Reis (1834–1874) publicly demonstrated the Reis telephone before the Physical Society of Frankfurt
  • 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.”
  • 28 December 1871 — Antonio Meucci files a patent caveat (n.3335) 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.
  • 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 — Gray invents a liquid transmitter for use with a telephone but does not build one.
  • 14 February 1876 — Elisha Gray files a patent caveat for transmitting the human voice through a telegraphic circuit.
  • 14 February 1876 — Alexander Bell applies for the patent "Improvements in Telegraphy", for electromagnetic telephones using undulating currents.
  • 19 February 1876 — Gray is notified by the U.S. Patent Office of an interference between his caveat and Bell's patent application.^ Landline telegraphs used a key to make or break an electrical circuit, a battery to produce power, a single line joining one telegraph station to another and an electromagnetic receiver or sounder that upon being turned on and off, produced a clicking noise.
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    ^ But CDMA does something like that, only using very low powered mobiles to reduce interference, and of course, some special coding.
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    ^ A telegraph key tap broke the circuit momentarily, transmitting a short pulse to a distant sounder, interpreted by an operator as a dot.
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    .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.^ (Time division duplexing, as used in cordless telephone schemes: DECT and Personal Handy Phone systems might have a place but this still isn't clear.
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    ^ The first point is that cell phones and base stations transmit or communicate with each other on dedicated paired frequencies called channels.
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    ^ The first law prohibits all drivers from using a handheld wireless telephone while operating a motor vehicle.

    .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 — Edison files for a patent on a carbon (graphite) transmitter.^ If you want to see the whole graphic at once then click here.
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    ^ Click here if you want an illustrated overview of cell site layout .
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    ^ Punch out the number that you want to call.
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    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

Modern emergency telephone powered by sound alone.
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.^ Noise: Other vehicles, electric power transmission, industrial processing, etc., create broadband noise that impairs the channel, especially at 150 MHz and below.
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.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.^ Even though Ethiopia was listed as a country with coverage, I just could not believe that it would actually work there.
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^ Apple s latest iPhone 3G will be more profitable than any other product in its line-up, which includes iPods, Macs, and iTunes.

^ It is much better than our cell phones we use everyday in Tennessee.
  • International Cell Phone and World Phones for Travel 31 January 2010 13:24 UTC www.mobal.com [Source type: General]

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.^ This allocation is split equally between wire-line and radio common carriers (each is allocated 333 channels).
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^ A standard T1 transmission link carrying a DS-1 signal transmits 24 voice channels of about 4kHz each.
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^ The FCC intends cellular service to be regulated by competition, with two competing system providers in each large city: a wire-line carrier and a radio common carrier.
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.Early telephones used a single wire for the subscriber's line, with ground return used to complete the circuit (as used in telegraphs).^ Landline telegraphs used a key to make or break an electrical circuit, a battery to produce power, a single line joining one telegraph station to another and an electromagnetic receiver or sounder that upon being turned on and off, produced a clicking noise.
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^ Early digital wireless used a similar method with the telegraph.
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.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.^ Every cell phone starts out with just one ESN. This number gets electronically burned into the phone's ROM, or read only memory chip.
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^ The TDMA based IS-136 uses puts three calls into the same 30kz channel space that AMPS uses to carry one call.
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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.^ One desirable feature of a mobile telephone system is the ability to roam; that is, subscribers must be able to call and be called in cities other than their home areas.
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.Users who wanted the ability to speak to several different locations would need to obtain and set up three or four pairs of telephones.^ They are so different (both in function and in how they are managed) that we never think of the set-up channel as the first of the cell's channels -- it's in a class by itself.
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^ At Mobal® we’ve chosen what we believe is the easiest system, which works in the same format wherever in the world you are — you never need to fiddle or set up your phone differently if you visit different countries — your Mobal® World Phone works seamlessly as you cross borders.
  • International Cell Phone and World Phones for Travel 31 January 2010 13:24 UTC www.mobal.com [Source type: General]

^ In this example, just below , the cell site transmits and receives on three different sets of channels, one for each part or sector of the three cells it covers.
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.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.^ Cellular One has shut down roaming "privileges" altogether in New York City, Washington and Miami at different times.
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^ Cellular Radio: Principles and Design, McGraw Hill, Inc., New York 1997 90.
  • Cellular Telephone Basics 16 September 2009 22:41 UTC www.privateline.com [Source type: FILTERED WITH BAYES]

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, 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").^ To prevent any possible cross-subsidization or favoritism, the Bell operating companies must offer their cellular service through separate subsidiaries.
  • Cellular Telephone Basics 16 September 2009 22:41 UTC www.privateline.com [Source type: FILTERED WITH BAYES]

^ The first law prohibits all drivers from using a handheld wireless telephone while operating a motor vehicle.

^ The efficient use of frequencies that results from the cellular approach permits Advanced Mobile Phone Service customers to enjoy a level of service almost unknown with present mobile telephone service.
  • Cellular Telephone Basics 16 September 2009 22:41 UTC www.privateline.com [Source type: FILTERED WITH BAYES]

.Telephones connected to the earliest Strowger 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.^ What's called "push to talk" since you must depress a microphone key or switch each time you want to talk.
  • Cellular Telephone Basics 16 September 2009 22:41 UTC www.privateline.com [Source type: FILTERED WITH BAYES]

^ One license went automatically to the local telephone companies, in telecom parlance, the local exchange carriers or LECs.
  • Cellular Telephone Basics 16 September 2009 22:41 UTC www.privateline.com [Source type: FILTERED WITH BAYES]

.Rural and other telephones that were not on a common battery exchange had a magneto or 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.^ This is unlike a landline telephone in which ringing gets produced at a central office or switch.
  • Cellular Telephone Basics 16 September 2009 22:41 UTC www.privateline.com [Source type: FILTERED WITH BAYES]

A U.S. candlestick telephone in use, circa 1915.
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 called a "ringer box." [3] 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, separate from the cradle base that housed the magneto crank and other parts.^ Once at the receiver the equipment identifies the call, separates its pieces from the spreading code and other calls, and returns the signal back to its original 9600 bit rate.
  • Cellular Telephone Basics 16 September 2009 22:41 UTC www.privateline.com [Source type: FILTERED WITH BAYES]

^ Using this method, a T1 line can carry 24 separate phone lines into your house or business with just an extra twisted pair.
  • Cellular Telephone Basics 16 September 2009 22:41 UTC www.privateline.com [Source type: FILTERED WITH BAYES]

^ It uses CDMA but is backward compatible with the analog based AMPS. IS-95 handles calls differently than TDMA schemes, although registration is the same.
  • Cellular Telephone Basics 16 September 2009 22:41 UTC www.privateline.com [Source type: FILTERED WITH BAYES]

.They were larger than the "candlestick" and more popular.^ In practice six sectors sites have been more trouble than they're worth.
  • Cellular Telephone Basics 16 September 2009 22:41 UTC www.privateline.com [Source type: FILTERED WITH BAYES]

^ Oh, and you have to perfectly control all customers so that they never attempt to use more resources than the system has available.
  • Cellular Telephone Basics 16 September 2009 22:41 UTC www.privateline.com [Source type: FILTERED WITH BAYES]

.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.^ Using this method, a T1 line can carry 24 separate phone lines into your house or business with just an extra twisted pair.
  • Cellular Telephone Basics 16 September 2009 22:41 UTC www.privateline.com [Source type: FILTERED WITH BAYES]

.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 sound proofed long distance telephone booth furnished with the latest technology.^ From the user's standpoint, calls are initiated and received as they would be from any business or residence telephone.
  • Cellular Telephone Basics 16 September 2009 22:41 UTC www.privateline.com [Source type: FILTERED WITH BAYES]

^ (Time division duplexing, as used in cordless telephone schemes: DECT and Personal Handy Phone systems might have a place but this still isn't clear.
  • Cellular Telephone Basics 16 September 2009 22:41 UTC www.privateline.com [Source type: FILTERED WITH BAYES]

^ Let's say you're making a long distance call.
  • Cellular Telephone Basics 16 September 2009 22:41 UTC www.privateline.com [Source type: FILTERED WITH BAYES]

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 Model 102. .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.^ And instead of using a wire to connect to a distant receiver, you've used electromagnetic waves, silently passing energy and the information it carries across the atmosphere.
  • Cellular Telephone Basics 16 September 2009 22:41 UTC www.privateline.com [Source type: FILTERED WITH BAYES]

^ That's since the mobile unit and the base station both need circuitry to transmit on one frequency while receiving on another.
  • Cellular Telephone Basics 16 September 2009 22:41 UTC www.privateline.com [Source type: FILTERED WITH BAYES]

^ It uses CDMA but is backward compatible with the analog based AMPS. IS-95 handles calls differently than TDMA schemes, although registration is the same.
  • Cellular Telephone Basics 16 September 2009 22:41 UTC www.privateline.com [Source type: FILTERED WITH BAYES]

.The circuit diagram of the Model 102 shows the direct connection of the receiver to the line, while the transmitter was induction coupled, with energy supplied by a local battery.^ And instead of using a wire to connect to a distant receiver, you've used electromagnetic waves, silently passing energy and the information it carries across the atmosphere.
  • Cellular Telephone Basics 16 September 2009 22:41 UTC www.privateline.com [Source type: FILTERED WITH BAYES]

The coupling transformer, battery, and ringer were in a separate enclosure. .The dial switch in the base interrupted the line current by repeatedly but very briefly disconnecting the line 1-10 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.^ Right now all digital cellular radio systems are second generation, prioritizing on voice traffic, circuit switching , and slow data transfer speeds.
  • Cellular Telephone Basics 16 September 2009 22:41 UTC www.privateline.com [Source type: FILTERED WITH BAYES]

^ To digress briefly, dial tone is not present on AMPS phones, although E.F. Johnson phones produced land line type dial tone within the unit.
  • Cellular Telephone Basics 16 September 2009 22:41 UTC www.privateline.com [Source type: FILTERED WITH BAYES]

After the 1930s, the base also enclosed the bell and induction coil, obviating the old separate ringer box. .Power was supplied to each subscriber line by central office batteries instead of a local battery, which required periodic service.^ Control equipment at the central office continually chooses an idle channel (if there is one) among the locally equipped complement of channels and marks it with an "idle" tone.
  • Cellular Telephone Basics 16 September 2009 22:41 UTC www.privateline.com [Source type: FILTERED WITH BAYES]

.For the next half century, the network behind the telephone became progressively larger and much more efficient, but after the dial was added the instrument itself changed little until American Telephone & Telegraph Company (AT&T) introduced Touch-Tone dialing in the 1960s.^ To progress from the early to the more mature configuration over a period of years, new cell sites can be added halfway between existing cell sites in stages.
  • Cellular Telephone Basics 16 September 2009 22:41 UTC www.privateline.com [Source type: FILTERED WITH BAYES]

^ And as American Morse code was a logical, cohesive plan to send signals, much more complicated and useful arrangements have been devised.
  • Cellular Telephone Basics 16 September 2009 22:41 UTC www.privateline.com [Source type: FILTERED WITH BAYES]

Digital telephony

.The Public Switched Telephone Network (PSTN) has gradually evolved towards digital telephony which has improved the capacity and quality of the network.^ Broad and deep knowledge of digital switching and transmission technology in the public switched telephone network, radio, signal processing, antennas, etc.
  • Cellular Telephone Basics 16 September 2009 22:41 UTC www.privateline.com [Source type: FILTERED WITH BAYES]

.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.^ Although first in each cell's lineup, most radio engineers place priority on the voice channels in a system.
  • Cellular Telephone Basics 16 September 2009 22:41 UTC www.privateline.com [Source type: FILTERED WITH BAYES]

^ An uncompressed, non-multiplexed, bandwidth hogging analog signal simply sounds better than its present day compressed, digital counterpart.
  • Cellular Telephone Basics 16 September 2009 22:41 UTC www.privateline.com [Source type: FILTERED WITH BAYES]

^ Using this method, a T1 line can carry 24 separate phone lines into your house or business with just an extra twisted pair.
  • Cellular Telephone Basics 16 September 2009 22:41 UTC www.privateline.com [Source type: FILTERED WITH BAYES]

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.
Later transmission methods such as SONET and fiber optic transmission further advanced digital transmission. .Although analog carrier systems existed that multiplexed multiple analog voice channels onto a single transmission medium, digital transmission allowed lower cost and more channels multiplexed on the transmission medium.^ A five digit code called the home system identification number (SID or sometimes SIDH) identifies the cellular carrier your phone is registered with.
  • Cellular Telephone Basics 16 September 2009 22:41 UTC www.privateline.com [Source type: FILTERED WITH BAYES]

^ If you ask an engineer in an AMPS system what channels he has on a cell, he'll automatically give you the voice channels.
  • Cellular Telephone Basics 16 September 2009 22:41 UTC www.privateline.com [Source type: FILTERED WITH BAYES]

^ [More bandwidth] "The most noticeable disadvantage that is directly associated with digital systems is the additional bandwidth necessary to carry the digital signal as opposed to its analog counterpart.
  • Cellular Telephone Basics 16 September 2009 22:41 UTC www.privateline.com [Source type: FILTERED WITH BAYES]

Today the end instrument often remains analog but the analog signals are typically converted to digital signals at the (Serving Area Interface (SAI), central office (CO), or other aggregation point. .Digital loop carriers (DLC) place the digital network ever closer to the customer premises, relegating the analog local loop to legacy status.^ Remember, too, that an analog wave carries this digital information, just like most modems.
  • Cellular Telephone Basics 16 September 2009 22:41 UTC www.privateline.com [Source type: FILTERED WITH BAYES]

^ IS-54 and now IS-136 co-exist with AMPS service, that is, a carrier can mix and match these digital and analog services on whatever channel sets they choose.
  • Cellular Telephone Basics 16 September 2009 22:41 UTC www.privateline.com [Source type: FILTERED WITH BAYES]

^ [More bandwidth] "The most noticeable disadvantage that is directly associated with digital systems is the additional bandwidth necessary to carry the digital signal as opposed to its analog counterpart.
  • Cellular Telephone Basics 16 September 2009 22:41 UTC www.privateline.com [Source type: FILTERED WITH BAYES]

IP telephony

Hardware-based IP phone.
.Internet Protocol (IP) telephony (also known as Voice over Internet Protocol, VoIP), is a disruptive technology that is rapidly gaining ground against traditional telephone network technologies.^ Broad and deep knowledge of digital switching and transmission technology in the public switched telephone network, radio, signal processing, antennas, etc.
  • Cellular Telephone Basics 16 September 2009 22:41 UTC www.privateline.com [Source type: FILTERED WITH BAYES]

.As of January 2005, up to 10% of telephone subscribers in Japan and South Korea have switched to this digital telephone service.^ Once the MTSO or mobile telephone switch assigns a voice channel the two frequencies making up the voice channel handle signaling during the actual conversation.
  • Cellular Telephone Basics 16 September 2009 22:41 UTC www.privateline.com [Source type: FILTERED WITH BAYES]

^ Broad and deep knowledge of digital switching and transmission technology in the public switched telephone network, radio, signal processing, antennas, etc.
  • Cellular Telephone Basics 16 September 2009 22:41 UTC www.privateline.com [Source type: FILTERED WITH BAYES]

A January 2005 Newsweek article suggested that Internet telephony may be "the next big thing."[4] As of 2006 many VoIP companies offer service to consumers and businesses.
.IP telephony uses an Internet connection and hardware IP Phones or softphones installed on personal computers to transmit conversations encoded as data packets.^ (Time division duplexing, as used in cordless telephone schemes: DECT and Personal Handy Phone systems might have a place but this still isn't clear.
  • Cellular Telephone Basics 16 September 2009 22:41 UTC www.privateline.com [Source type: FILTERED WITH BAYES]

^ Demultiplexing those conversations is no more difficult than adding the right circuit board to a personal computer.
  • Cellular Telephone Basics 16 September 2009 22:41 UTC www.privateline.com [Source type: FILTERED WITH BAYES]

^ We couldn't connect thru the internet but the Mobal World Phone worked just fine.
  • International Cell Phone and World Phones for Travel 31 January 2010 13:24 UTC www.mobal.com [Source type: General]

.In addition to replacing POTS (plain old telephone service), IP telephony services are also competing with mobile phone services by offering free or lower cost connections via WiFi hotspots.^ The latter is responsible for the high voice quality and high signaling reliability of the Advanced Mobile Phone Service.
  • Cellular Telephone Basics 16 September 2009 22:41 UTC www.privateline.com [Source type: FILTERED WITH BAYES]

^ More recent systems (the MJ system at 150 KHz and the MK system at 450 KHz) [ Improved Mobile Telephone Service or IMTS, ed.
  • Cellular Telephone Basics 16 September 2009 22:41 UTC www.privateline.com [Source type: FILTERED WITH BAYES]

^ Here's some great reading on the transition from mobile telephone service to cellular.
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VoIP is also used on private networks which may or may not have a connection to the global telephone network.
IP telephones have two 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 will cease to function during a power outage as can occur during an emergency or disaster, exactly when the phone is most needed.^ Once the MTSO or mobile telephone switch assigns a voice channel the two frequencies making up the voice channel handle signaling during the actual conversation.
  • Cellular Telephone Basics 16 September 2009 22:41 UTC www.privateline.com [Source type: FILTERED WITH BAYES]

^ A mobile phone runs a self diagnostic when it's powered up.
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^ Verizon Wireless has just added a new mobile phone in its line-up useful and powerful mobile handsets.

.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's a prolonged power black-out.^ As we rely more heavily on mobile phones to stay connected, they increasingly know everything about us and have b...

^ Since there were so many qualified applicants, operating licenses were ultimately granted by the luck of a draw, not by a spectrum auction as they are today.
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^ The two Spanish speakers can hear each other talking with out a problem, since their language or 'code' is so specific.
  • Cellular Telephone Basics 16 September 2009 22:41 UTC www.privateline.com [Source type: FILTERED WITH BAYES]

.A second distinct problem for an IP phone is the lack of a 'fixed address' which can impact the provision of emergency services such as police, fire or ambulance, should someone call for them.^ Making a call and getting a call from your cellular phone should be equally easy.
  • Cellular Telephone Basics 16 September 2009 22:41 UTC www.privateline.com [Source type: FILTERED WITH BAYES]

^ NAMPS had the same fading problems as AMPS, lacked the error correction that digital systems provided and wasn't sophisticated enough to handle encryption or advanced services.
  • Cellular Telephone Basics 16 September 2009 22:41 UTC www.privateline.com [Source type: FILTERED WITH BAYES]

^ Things such as calling number identification, extension phone service and messaging.
  • Cellular Telephone Basics 16 September 2009 22:41 UTC www.privateline.com [Source type: FILTERED WITH BAYES]

.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.^ Comes with an easy to follow user guide - giving you Mobal's global cell phone service with no monthly fees on your own cell phone!
  • International Cell Phone and World Phones for Travel 31 January 2010 13:24 UTC www.mobal.com [Source type: General]

^ In the international cell phone industry many new companies and services appear and disappear, leaving their customers searching for a replacement.
  • International Cell Phone and World Phones for Travel 31 January 2010 13:24 UTC www.mobal.com [Source type: General]

Fixed telephone lines per 100 inhabitants 1997-2007

Usage

By the end of 2006, there were a total of nearly 4 billion mobile and fixed-line subscribers worldwide. This included 1.27 billion fixed-line subscribers and 2.68 billion mobile subscribers. [5]

Telephone operating companies

.In some countries, many telephone operating companies (commonly abbreviated to telco in American English) are in competition to provide telephone services.^ CDMA is a part of an overall operating system that provides cellular radio service.
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^ The FCC intends cellular service to be regulated by competition, with two competing system providers in each large city: a wire-line carrier and a radio common carrier.
  • Cellular Telephone Basics 16 September 2009 22:41 UTC www.privateline.com [Source type: FILTERED WITH BAYES]

^ Perhaps the biggest is, how many cellular companies (carriers) provide service to your location?
  • Cellular Telephone Basics 16 September 2009 22:41 UTC www.privateline.com [Source type: FILTERED WITH BAYES]

.The above Main article lists only facilities based providers and not companies which lease services from facilities based providers in order to serve their customers.^ When a system is newly installed in an area (when large cells are serving only a few customers), frequency reuse is unnecessary.
  • Cellular Telephone Basics 16 September 2009 22:41 UTC www.privateline.com [Source type: FILTERED WITH BAYES]

^ Perhaps the biggest is, how many cellular companies (carriers) provide service to your location?
  • Cellular Telephone Basics 16 September 2009 22:41 UTC www.privateline.com [Source type: FILTERED WITH BAYES]

^ If only 30% of your customers can use it, does it really provide capacity gains?
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Patents

.
  • US 174,465 -- Telegraphy (Bell's first telephone patent) -- 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 (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. 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.^ Since cellular uses radio waves to communicate signals are subject to the vagaries of the radio band.
    • Cellular Telephone Basics 16 September 2009 22:41 UTC www.privateline.com [Source type: FILTERED WITH BAYES]

    ^ It's tough transferring a call between cells in any cellular radio system.
    • Cellular Telephone Basics 16 September 2009 22:41 UTC www.privateline.com [Source type: FILTERED WITH BAYES]

    ^ The mobile sends its phone number, its electronic serial number, and its home system ID. Among other things.
    • Cellular Telephone Basics 16 September 2009 22:41 UTC www.privateline.com [Source type: FILTERED WITH BAYES]

    (Motorola)

See also

Notes

References

Further reading

  • Sobel, Robert (1974), The Entrepreneurs: Explorations Within the American Business Tradition. Weybright & Talley. .ISBN 0-679-40064-8.
  • Todd, Kenneth P. (1998), A Capsule History of the Bell System.^ This is from the long out of print A History of Engineering and Science in the Bell System: Communications Sciences (1925 -- 1980), prepared by members of the technical staff, AT&T Bell Laboratories, c.
    • Cellular Telephone Basics 16 September 2009 22:41 UTC www.privateline.com [Source type: FILTERED WITH BAYES]

    ^ A History of Engineering and Science in the Bell System: Communications Sciences (1925 -- 1980) .
    • Cellular Telephone Basics 16 September 2009 22:41 UTC www.privateline.com [Source type: FILTERED WITH BAYES]

    American Telephone & Telegraph Company (AT&T).

External links


Citable sentences

Up to date as of December 02, 2010

Here are sentences from other pages on Mobile phone, which are similar to those in the above article.








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