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0236 là mã vùng ở đâu ???

Mã vùng thông tin 0236

Mã vùng 0236 là gì? Mã vùng 0236 thuộc thành phố nào? Có nhiều bạn quan tâm đến câu hỏi này nên hôm nay edanhba xin giải đáp thắc mắc của các bạn.  0236 là mã vùng mới của Thành phố Đà Nẵng. Thành phố Đà Nẵng đổi mã vùng 0511 thành 0236

Để dễ dàng quản lý và lưu trữ kho tài nguyên mã vùng, Bộ Thông tin Truyền thông đã quyết định thay đổi mã vùng các tỉnh, thành phố Việt Nam theo Quyết định 2036 / QĐ-BTTTT. Và thành phố Đà Nẵng cũng không ngoại lệ. Thành phố Đà Nẵng đổi mã vùng 0511 thành 0236. Thay đổi này được thực hiện từ tháng 07/2017. Mã vùng Đà Nẵng cũ 0511

Đầu số 0511 là mã vùng cũ của Thành phố Đà Nẵng. đầu số mới là 0236  Mã vùng mới thành phố Đà Nẵng 0236

Đầu số 0236 là mã vùng gần đây nhất của Thành phố Đà Nẵng. Đầu số này chính thức được sử dụng từ tháng 07/2017 thay thế cho đầu số 0511 cũ.  Cách sử dụng đầu số 0236 thay cho 0511

Dưới đây chúng tôi xin hướng dẫn các bạn cách quay số theo mã vùng của Thành phố Đà Nẵng tính đến tháng 7/2017

Bạn đang ở nước ngoài   : Bạn phải sử dụng cú pháp sau:
00 + 84 + [mã vùng] + [số điện thoại]
[+] + 84 + [mã vùng] + [số điện thoại]

Bạn đang sử dụng điện thoại di động tại Việt Nam   : Bạn phải sử dụng cú pháp sau
0 + [mã vùng] + [số điện thoại]

Các bạn ở Việt Nam ngoại tỉnh   : Dùng cú pháp sau
0 + [mã vùng] + [số điện thoại]

Bạn ở cùng tỉnh thành Việt Nam   : Bạn phải sử dụng cú pháp
[số điện thoại]  Danh sách mã vùng 64 tỉnh thành Việt Nam được cập nhật mới nhất 2020

Lưu ý: Các mã vùng cũ là mã vùng đã được sử dụng trước ngày 17/06/2017. Sau ngày 17/6/2017, các đầu số điện thoại cố định của các tỉnh, thành phố sẽ được chuyển đổi mã vùng mới. Cụ thể, có 4 tỉnh, thành phố chưa thay đổi số điện thoại cố định là Vĩnh Phúc (211), Phú Thọ (210), Hòa Bình (218) và Hà Giang (219).

Googol

Từ Wikipedia, bách khoa toàn thư miễn phí Chuyển tới điều hướng Chuyển tới tìm kiếm Không được nhầm lẫn với Google hoặc Nikolai Gogol.

Một   googol   là số lượng lớn   10  100  . Trong ký hiệu thập phân, nó được viết dưới dạng số 1 theo sau là một trăm số không:   10, 000, 000, 000, 000, 000, 000, 000, 000, 000, 000, 000, 000, 000, 000, 000 000, 000, 000, 000, 000, 000, 000, 000, 000, 000, 000, 000, 000, 000, 000, 000.  từ nguyên học

Thuật ngữ này được đặt ra vào năm 1920 bởi Milton Sirotta, chín tuổi (1911-1981), cháu trai của nhà toán học người Mỹ Edward Kasner.  [1]   Kasner đã  phổ biến khái niệm này trong cuốn sách Toán học và Trí tưởng tượng năm 1940 của ông  .  [2]   Các tên khác của số tiền này là   mười Duotriginillionen   trên quy mô ngắn,   mười nghìn Sexdezillion   trên quy mô dài, hoặc   mười Sexdezillion   trên quy mô dài Peletier   .  kích cỡ

Một googol không có ý nghĩa đặc biệt trong toán học. Tuy nhiên, nó rất hữu ích khi so sánh với các số lượng rất lớn khác như số lượng hạt hạ nguyên tử trong vũ trụ khả kiến ​​hoặc số khả năng giả định trong một ván cờ. Kasner đã sử dụng nó để minh họa sự khác biệt giữa một số lớn không thể tưởng tượng được và vô hạn, và với khả năng đó, nó đôi khi được sử dụng trong các lớp học toán. Để có cảm giác về một googol thực sự lớn như thế nào,   có thể so sánh khối lượng của một electron gần 10 –  30 kg với khối lượng của vũ trụ nhìn thấy, ước tính vào khoảng 10  50   đến 10  60   kg.  [3]  Nó là một tỷ lệ theo thứ tự trong khoảng 10  80   đến 10  90 , hoặc nhiều nhất là một phần mười tỷ của googol (0,000000001% của googol).

Carl Sagan đã chỉ ra rằng tổng số hạt cơ bản trong vũ trụ là khoảng 10  80   (số Eddington) và rằng nếu toàn bộ vũ trụ đã được lấp đầy với neutron để có không gian nơi nào trống, sẽ có khoảng 10  128  . Ông cũng nhận thấy sự tương tự của phép tính thứ hai với phép tính của Archimedes trong   Người đếm cát  . Theo tính toán của Archimedes, nếu vũ trụ của Aristarchus (đường kính khoảng 2 năm ánh sáng) hoàn toàn chứa đầy cát, nó sẽ   chứa 10  63 hạt. Nếu vũ trụ quan sát được lớn hơn nhiều ngày nay bị lấp đầy bởi cát, nó sẽ vẫn chỉ là 10  95  Hạt diêm mạch. 100.000 vũ trụ đầy cát có thể quan sát được khác sẽ là cần thiết để tạo ra một googol. [4]

Thời gian phân rã của một lỗ đen siêu lớn có khối lượng bằng 1 thiên hà (10  11   lần khối lượng Mặt Trời) do bức xạ Hawking là 10  100   năm. [5]   Do đó, nhiệt độ chết của một vũ trụ đang giãn nở được giới hạn để xảy ra ít nhất một năm googoles trong tương lai. tính chất

Một googol là khoảng   70!  (giai thừa của 70). [a]   Sử dụng một số nguyên, hệ thống số nhị phân, người ta sẽ cần 333 bit để biểu diễn một googol, tức là 1 googol =   2 ^ {(100 / \ mathrm {log} _ {10} 2)} ≈ 2  332.19280949  . Tuy nhiên, googol nằm trong giới hạn tối đa của loại dấu phẩy động với độ chính xác kép theo IEEE 754, nhưng không có độ chính xác đầy đủ trong phần định trị.

Sử dụng số học mô-đun, chuỗi các phần còn lại (mod   n  ) của googol bắt đầu bằng mod 1 như sau: 0, 0, 1, 0, 0, 4, 4, 0, 1, 0, 1, 4, 3, 4 , 10, 0, 4, 10, 9, 0, 4, 12, 13, 16, 0, 16, 10, 4, 16, 10, 5, 0, 1, 4, 25, 28, 10, 28, 16 , 0, 1, 4, 31, 12, 10, 36, 27, 16, 11, 0, … (chuỗi A066298 trong OEIS)

Trình tự này giống như trình tự của các phần còn lại (mod n) của một Googolplex cho đến vị trí thứ 17. Ảnh hưởng văn hoá

Tên của từ được sử dụng rộng rãi bởi tên công ty Google, tên “Google” là một lỗi chính tả tình cờ của “googol” bởi những người sáng lập công ty  [6],   được chọn để báo hiệu rằng công cụ tìm kiếm tuyệt vời nên cung cấp số lượng của thông tin. [7]   Năm 2004, các thành viên gia đình của Kasner, những người được thừa kế quyền đối với cuốn sách của ông, đã cân nhắc việc kiện Google vì đã sử dụng thuật ngữ googol; [8]   Tuy nhiên, không có vụ kiện nào được nộp đơn. [  Yêu cầu trích dẫn  ]

Kể từ tháng 10 năm 2009, Google đã chỉ định tên miền máy chủ của mình theo miền “1e100.net”, ký hiệu khoa học cho 1 googol, nhằm cung cấp một miền duy nhất để xác định các máy chủ trong mạng Google. [9]  [10]

Từ này nổi bật vì nó xuất hiện trong một tập của chương trình đố vui Ai muốn trở thành triệu phú của Vương quốc Anh   khi ứng cử viên Charles Ingram gian lận trong suốt chương trình với sự giúp đỡ của một đồng minh trong khán giả trường quay. [11]  Xem thêm

  • Googolplex
  • Số của Graham
  • Skewes số
  • vô cực
  • Những cái tên có số lượng lớn

Nhận xét

  1. ^   1,1979 × 10  100

Người giới thiệu

  1. ^  Bialik, Carl (14. Juni 2004). „Ohne Edward Kasner könnte es kein Google geben“. Das Wall Street Journal Online . Archiviert vom Original am 30. November 2016. (abgerufen am 17. März 2015)
  2. ^ Kasner, Edward; Newman, James R. (1940). Mathematics and the Imagination. Simon and Schuster, New York. ISBN 0-486-41703-4. Archived from the original on 2014-07-03. The relevant passage about the googol and googolplex, attributing both of these names to Kasner’s nine-year-old nephew, is available in James R. Newman, ed. (2000) [1956]. The world of mathematics, volume 3. Mineola, New York: Dover Publications. pp. 2007–2010. ISBN 978-0-486-41151-4.
  3. ^ McPherson, Kristine (2006). Elert, Glenn (ed.). “Mass of the universe”. The Physics Factbook. Retrieved 2019-08-24.
  4. ^ Sagan, Carl (1981). Cosmos. Book Club Associates. pp. 220–221.
  5. ^ Page, Don N. (1976-01-15). “Particle emission rates from a black hole: Massless particles from an uncharged, nonrotating hole”. Physical Review D. American Physical Society (APS). 13 (2): 198–206. Bibcode:1976PhRvD..13..198P. doi:10.1103/physrevd.13.198. ISSN 0556-2821. See in particular equation (27).
  6. ^ Koller, David (January 2004). “Origin of the name “Google””. Stanford University. Archived from the original on July 4, 2012. Retrieved July 4, 2012.
  7. ^ “Google! Beta website”. Google, Inc. Archived from the original on February 21, 1999. Retrieved October 12, 2010.
  8. ^ “Have your Google people talk to my ‘googol’ people”. Archived from the original on 2014-09-04.
  9. ^ Cade Metz (8 February 2010). “Google doppelgänger casts riddle over interwebs”. The Register. Archived from the original on 3 March 2016. Retrieved 30 December 2015.
  10. ^ “What is 1e100.net?”. Google Inc. Archived from the original on 9 January 2016. Retrieved 30 December 2015.
  11. ^ Falk, Quentin; Falk, Ben (2005), “A Code and a Cough: Who Wants to Be a Millionaire? (1998–)”, Television’s Strangest Moments: Extraordinary But True Tales from the History of Television, Franz Steiner Verlag, pp. 245–246, ISBN 9781861058744.

External links

  • Weisstein, Eric W. “Googol”. MathWorld.
  • Googol at PlanetMath.
  • Padilla, Tony; Symonds, Ria. “Googol and Googolplex”. Numberphile. Brady Haran. Archived from the original on 2014-03-29. Retrieved 2013-04-06.
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Telephone

From Wikipedia, the free encyclopediaJump to navigation Jump to search”Phone” redirects here. For the handheld personal computer, see Smartphone. For other uses, see Phone (disambiguation) and Telephone (disambiguation).

A rotary dial telephone, c. 1940sAT&T push button telephone made by Western Electric, model 2500 DMG black, 1980

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telephone 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. The term is derived from Greek: τῆλε (tēlefar) and φωνή (phōnēvoice), together meaning distant voice. A common short form of the term is phone, which came into use almost immediately after the first patent was issued.[1]

In 1876, Alexander Graham Bell was the first to be granted a United States patent for a device that produced clearly intelligible replication of the human voice at a second device.[2] This instrument was further developed by many others, and became rapidly indispensable in business, government, and in households.

The essential elements of a telephone are a microphone (transmitter) to speak into and an earphone (receiver) which reproduces the voice in a distant location.[3] In addition, most telephones contain a ringer to announce an incoming telephone call, and a dial or keypad to enter a telephone number when initiating a call to another telephone. 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 simultaneously.

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

Convergence has given most modern cell phones capabilities far beyond simple voice conversation. Most are smartphones, integrating all mobile communication and many computing needs.Basic principlesSchematic 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 (A5). Until the 1960s dials used almost exclusively the rotary technology, which was replaced by dual-tone multi-frequency signaling (DTMF) with pushbutton telephones.

A major expense of wire-line telephone service is the outside wire plant. Telephones transmit both 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 for 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 operationFurther information: Telephone call

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.

To place a telephone call, the calling party picks up the telephone’s handset, thereby operating a lever that closes the hook switch (A4). This powers the telephone by connecting the transmission hybrid transformer, as well as the transmitter (microphone) and receiver (speaker) to the line. In this off-hook state, the telephone circuitry has a low resistance of typically less than 300 ohms, which causes the flow of direct current (DC) in the line (C) from the telephone exchange. The exchange detects this current, attaches a digit receiver circuit to the line, and sends dial tone to indicate its readiness. On a modern push-button telephone, the caller then presses the number keys to send the telephone number of the destination, the called party. The keys control a tone generator circuit (not shown) that sends DTMF tones to the exchange. A rotary-dial telephone uses pulse dialing (A5), sending electrical pulses, that the exchange counts to decode each digit of the telephone number. If the called party’s line is available, the terminating exchange applies an intermittent alternating current (AC) ringing signal of 40 to 90 volts to alert the called party of the incoming call. If the called party’s line is in use, however, the exchange returns a busy signal to the calling party. If the called party’s line is in use but subscribes to call waiting service, the exchange sends an intermittent audible tone to the called party to indicate another call.

The electromechanical ringer of a telephone (A7) is connected to the line through a capacitor (A6), which blocks direct current and passes the alternating current of the ringing power. 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 alternating current down the line to activate the ringer and announce an incoming call. In manual service exchange areas, before dial service was installed, telephones had hand-cranked magneto generators 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.[4] 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 disconnect the alerting device and connect 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 the transmitter.

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 microphone.

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 (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 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 infrastructure components.Early historyMain article: History of the telephoneFurther information: Invention of the telephone and Elisha Gray and Alexander Bell telephone controversyAlexander Graham Bell’s Telephone Patent DrawingReplica of the telettrofono, invented by Antonio Meucci and credited by several sources as the first telephone. [5]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”. Perhaps the earliest use of the word for a communications system was the telephon created by Gottfried Huth in 1796. Huth proposed an alternative to the optical telegraph of Claude Chappe in which the operators in the signaling towers would shout to each other by means of what he called “speaking tubes”, but would now be called giant megaphones.[6] A communication device for sailing vessels called a “telephone” was invented by Captain John Taylor in 1844. This instrument used four air horns to communicate with vessels in foggy weather.[7][8]

Johann Philipp Reis used the term in reference to his invention, commonly known as the Reis telephone, in c. 1860. His device appears to be the first device based on the conversion of sound into electrical impulses. The term telephone was adopted into the vocabulary of many languages. It is derived from the Greek: τῆλε, tēle, “far” and φωνή, phōnē, “voice”, together meaning “distant voice”.

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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.[9][4]

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

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

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

Timeline of early development

Main article: Timeline of the telephoneReis’s telephoneBell’s first telephone transmitter, ca. 1876, reenacted 50 years laterAcoustic telephone ad, The Consolidated Telephone Co., Jersey City, New Jersey, 18861896 telephone from SwedenWooden wall telephone with a hand-cranked magneto generator

  • 1844: Innocenzo Manzetti first mooted the idea of a “speaking telegraph” or telephone. Use of the “speaking telegraph” and “sound telegraph” monikers would eventually be replaced by the newer, distinct name, “telephone”.
  • 26 August 1854: Charles Bourseul published an article in the magazine L’Illustration (Paris): “Transmission électrique de la parole” (electric transmission of speech), describing a “make-and-break” type telephone transmitter later created by Johann Reis.
  • 26 October 1861: Johann Philipp Reis (1834–1874) publicly demonstrated the Reis telephone before the Physical Society of Frankfurt.[4] Reis’s telephone was not limited to musical sounds. Reis also used his telephone to transmit the phrase “Das Pferd frisst keinen Gurkensalat” (“The horse does not eat cucumber salad”).
  • 22 August 1865, La Feuille d’Aoste reported “It is rumored that English technicians to whom 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 U.S. Patent Office titled “Sound Telegraph”, describing communication of voice between two people by wire. A ‘patent caveat’ was not an invention patent award, but only an unverified notice filed by an individual that he or she intends to file a 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 the telephone but does not build one.
  • 14 February 1876: Gray files a patent caveat for transmitting the human voice through a telegraphic circuit.
  • 14 February 1876: Alexander Graham Bell applies for the patent “Improvements in Telegraphy”, for electromagnetic telephones using what is now called amplitude modulation (oscillating current and voltage) but which he referred to as “undulating current”.
  • 19 February 1876: Gray is notified by the U.S. Patent Office of an interference between his caveat and Bell’s patent application. Gray decides to abandon his caveat.
  • 7 March 1876: Bell’s U.S. patent 174,465 “Improvement in Telegraphy” is granted, covering “the method of, and apparatus for, transmitting vocal or other sounds telegraphically…by causing electrical undulations, similar in form to the vibrations of the air accompanying the said vocal or other sound.”
  • 10 March 1876: The first successful telephone transmission of clear speech using a liquid transmitter when Bell spoke into his device, “Mr. Watson, come here, I want to see you.” and Watson heard each word distinctly.
  • 30 January 1877: Bell’s U.S. patent 186,787 is granted for an electromagnetic telephone using permanent magnets, iron diaphragms, and a call bell.
  • 27 April 1877: 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 more expensive.

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

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 the century.

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 signal.

In the 1890s a new smaller style of telephone was introduced, packaged in three parts. The transmitter stood on a stand, known as a “candlestick” for its shape. When not in use, the receiver hung on a hook with a switch in it, known as a “switchhook”. Previous telephones required the user to operate a separate switch to connect either the voice or the bell. With the new kind, the user was less likely to leave the phone “off the hook”. In phones connected to magneto exchanges, the bell, induction coil, battery and magneto were in a separate bell box or “ringer box”.[16] 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 technology.

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.[17] 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.

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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 Telephone & Telegraph Company (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, Philippines)
  •  Play mediaVideo shows the operation of an Ericofon
  • Modern sound-powered emergency telephone
  • One type of mobile phone, called a cell phone

Digital telephones and voice over IPMain articles: Digital telephony and Voice over IPAn IP desktop telephone attached to a computer network, with touch-tone dialingFixed 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, over the next several decades. With the development of stored program control and MOS integrated circuits for electronic switching systems, and new transmission technologies such as pulse-code modulation (PCM), telephony gradually evolved towards digital telephony, which improved the capacity, quality, and cost of the network.[18]

The development of digital data communications methods made it possible to digitize voice and transmit it as real-time data across computer networks and the Internet, giving rise to the field of Internet Protocol (IP) telephony, also known as voice over 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 infrastructure.

By January 2005, up to 10% of telephone subscribers in Japan and South Korea had switched to this digital telephone service. A January 2005 Newsweek article suggested that Internet telephony may be “the next big thing.”[19] The technology has spawned a new industry comprising many VoIP companies that offer services to consumers and businesses. The reported global VoIP market in October 2021 was $85.2 billion with a projection of $102.5 billion by 2026.[20]

IP telephony uses high-bandwidth Internet connections and specialized customer premises equipment to transmit telephone calls via the Internet, or any modern private data network. The customer equipment may be an analog telephone adapter (ATA) which translates the signals of a conventional analog telephone to packet-switched IP messages. IP Phones have these functions combined in a standalone device, and computer softphone applications use microphone and headset devices of a personal computer.

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

In 2002, only 10% of the world’s population used mobile phones and by 2005 that percentage had risen to 46%.[21] 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.[22]See also

  • Telephones portal
  • Bell System
  • Bell Telephone Memorial
  • Cordless telephone
  • Harvard sentences
  • Index of telephone-related articles
  • Jipp curve
  • List of telephone operating companies
  • Party line (telephony)
  • Phone hacking
  • Satellite phone
  • Spamming
  • Telephone keypad
  • Telephone jack and plug
  • Telephone tapping
  • Tip and ring
  • Videophone

References

  1. ^ “Etymology of the word “phone””.
  2. ^ “Who Is Credited With Inventing the Telephone”. Library of Congress.
  3. ^ “United States Coast Guard Sound-Powered Telephone Talkers Manual, 1979, p. 1″ (PDF).
  4. ^ Jump up to: a b c Kempe, Harry Robert; Garcke, Emile (1911). “Telephone” . In Chisholm, Hugh (ed.). Encyclopædia Britannica26 (11th ed.). Cambridge University Press. pp. 547–57.
  5. ^ Carroll, Rory (June 17, 2002). “Bell did not invent telephone, US rules” – via www.theguardian.com.
  6. ^ Holzmann, Gerard J.; Pehrson, Björn, The Early History of Data Networks, pp. 90-91, Wiley, 1995 ISBN 0818667826.
  7. ^ The Year-book of Facts in Science and Art. Simpkin, Marshall, and Company. July 6, 1845. p. 55 – via Internet Archive.
  8. ^ “The Telephone and Telephone Exchanges” by J. E. Kingsbury published in 1915.
  9. ^ Coe, Lewis (1995). The Telephone and Its Several Inventors: A History. Jefferson, NC: McFarland & Company, Inc. p. 5. ISBN 978-0-7864-2609-6.
  10. ^ Brown, Travis (1994). Historical first patents: the first United States patent for many everyday things (illustrated ed.). University of Michigan: Scarecrow Press. p. 179. ISBN 978-0-8108-2898-8.
  11. ^ Beauchamp, Christopher (2010). “Who Invented the Telephone?: Lawyers, Patents, and the Judgments of History”. Technology and Culture39: 858–859 – via Project MUSE.
  12. ^ US 174465 Alexander Graham Bell: “Improvement in Telegraphy” filed on February 14, 1876, granted on March 7, 1876.
  13. ^ “Puskás, Tivadar”. Omikk.bme.hu. Retrieved 2010-05-23.
  14. ^ Rick Jolly (2018). Jackspeak: A guide to British Naval slang & usage. p. 46. ISBN 9781472834140.
  15. ^ “on the horn”. Merriam-Webster. Retrieved 25 August 2021.
  16. ^ “Ringer Boxes”. Telephonymuseum.com. Archived from the original on 2001-10-12. Retrieved 2010-05-23.
  17. ^ Circuit Diagram, Model 102, Porticus Telephone website.
  18. ^ Allstot, David J. (2016). “Switched Capacitor Filters”. In Maloberti, Franco; Davies, Anthony C. (eds.). A Short History of Circuits and Systems: From Green, Mobile, Pervasive Networking to Big Data Computing (PDF). IEEE Circuits and Systems Society. pp. 105–110. ISBN 9788793609860.
  19. ^ Sheridan, Barrett. “Newsweek – National News, World News, Health, Technology, Entertainment and more…” MSNBC. Archived from the original on January 18, 2005. Retrieved 2010-05-23.
  20. ^ “Global VoIP Services Market 2021-2026”. Research and Markets. October 2021.
  21. ^ “Are Cell Phones Ruining Our Social Skills? – SiOWfa15: Science in Our World: Certainty and Controversy”. sites.psu.edu.
  22. ^ Next-Generation Networks Set to Transform Communications, International Telecommunications Union website, 4 September 2007. Retrieved 5 July 2009.

Further reading

  • Brooks, John (1976). Telephone: The first hundred years. HarperCollins.
  • Bruce, Robert V. (1990). Bell: Alexander Graham Bell and the Conquest of Solitude. Cornell University Press. ISBN 978-0-8014-9691-2.
  • Casson, Herbert Newton. (1910) The history of the telephone online.
  • Coe, Lewis (1995). Điện thoại và một số nhà phát minh: Lịch sử.  Jefferson, NC: McFarland & Co.
  • Evenson, A. Edward (2000). Âm mưu cấp bằng sáng chế điện thoại năm 1876: Cuộc tranh cãi của Elisha Grey – Alexander Bell.  Jefferson, NC: McFarland & Co.
  • Fischer, Claude S. (1994)  Mỹ gọi: Lịch sử xã hội của điện thoại đến năm 1940  (Univ of California Press, 1994)
  • Huurdeman, Anton A. (2003). Lịch sử Toàn cầu về Viễn thông  Hoboken: NJ: Wiley-IEEE Press.
  • John, Richard R. (2010). Network Nation: Phát minh ra Viễn thông Mỹ.  Cambridge, MA: Nhà xuất bản Đại học Harvard.
  • MacDougall, Robert. Mạng lưới nhân dân: Nền kinh tế chính trị của điện thoại trong thời đại vàng son.  Philadelphia: Nhà xuất bản Đại học Pennsylvania.
  • Muller, Milton. (1993) “Dịch vụ phổ quát trong lịch sử điện thoại: Tái thiết.” Telekommunikationspolitik   17.5 (1993): 352-69.
  • Todd, Kenneth P. (1998),   Lịch sử viên nang của hệ thống chuông  . Công ty Điện thoại và Điện báo Hoa Kỳ (AT&T).

liện kết ngoại

  • Dữ liệu ban đầu của ngành điện thoại Hoa Kỳ
  • “Điện thoại”. Từ điển Bách khoa Quốc tế mới   . Năm 1905.
  • Kempe, Harry Robert; Garcke, Emile (1911). “Điện thoại”. Bách khoa toàn thư Britannica   . 26   (ấn bản thứ 11). Trang 547-557.
  • Bảo tàng ảo về điện thoại sơ khai
  • Điện thoại, 1877
  • Phim ngắn   “Now You’re Talking (1927)” có thể   được tải xuống miễn phí từ Internet Archive.
  • Phim ngắn   “Kommunikation (1928)” có thể   được tải xuống miễn phí từ Internet Archive.
  • Có   thể tải xuống miễn phí phim ngắn   “Ký ức điện thoại (Reel 1 of 2) (1931)” từ Internet Archive.
  • Phim ngắn   “Ký ức điện thoại (Reel 2 of 2) (1931)” có thể   được tải xuống miễn phí từ Internet Archive.
  • Phim ngắn   “Far Speaking (khoảng năm 1935)” có thể   được tải xuống miễn phí từ Internet Archive.
  • “Hoa Kỳ 174.465”. pdfpiw.uspto.gov   .   – Telegraphy   (Bằng sáng chế điện thoại đầu tiên của Bell) —Alexander Graham Bell
  • US 186.787 – Điện báo   (Máy thu nam châm   vĩnh viễn) – Alexander Graham Bell
  • Hoa Kỳ 474.230 –   Điện báo nói   (máy phát than chì) – Thomas Edison
  • Điện thoại nói chuyện 203.016 Hoa Kỳ     (Máy phát nút carbon) —Thomas Edison
  • US 222390 –   Điện thoại   carbon (máy phát hạt carbon) -Thomas Edison
  • Điện thoại 485.311 Hoa Kỳ   (Máy phát carbon rắn   ) – Anthony C. White (Kỹ sư Bell) Thiết kế này được sử dụng cho đến năm 1925 và điện thoại đã lắp đặt được sử dụng cho đến những năm 1940.
  • Hoa Kỳ 3.449.750 –    Thiết bị  liên lạc và tín hiệu vô tuyến   song công —GH Sweigert
  • Hoa Kỳ 3.663.762 – Hệ thống   thông tin di động di động –   Amos Edward Joel (Bell Labs)
  • Hoa Kỳ 3,906,166 – Hệ thống điện   thoại vô tuyến   (DynaTAC Handy) -Martin Cooper et al. (Motorola)
showvte viễn thông

Thể loại:

  • 1876 ​​lời giới thiệu
  • Phát minh của mỹ
  • Phát minh của Canada
  • Tranh cãi về Khám phá và Phát minh
  • Phát minh của Đức
  • Phát minh của người Scotland
  • thiết bị văn phòng
  • Thiết bị viễn thông
  • Điện thoại
  • đồ gia dụng
  • Phát minh thế kỷ 19

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