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Encyclopedia > Modem

Modem (from modulator-demodulator) is a device that modulates an analog carrier signal to encode digital information, and also demodulates such a carrier signal to decode the transmitted information. The goal is to produce a signal that can be transmitted easily and decoded to reproduce the original digital data. Modems can be used over any means of transmitting analog signals, from driven diodes to radio. Look up modem in Wiktionary, the free dictionary. ... In computer hardware, a peripheral device is any device attached to a computer in order to expand its functionality. ... For other uses, see Modulation (disambiguation). ... This article or section does not adequately cite its references or sources. ... In information theory, a signal is the sequence of states of a communications channel that encodes a message. ... For other uses, see Digital (disambiguation). ... Demodulation is the act of removing the modulation from an analog signal. ... For other uses, see Data (disambiguation). ... Closeup of the image below, showing the square shaped semiconductor crystal various semiconductor diodes, below a bridge rectifier Structure of a vacuum tube diode In electronics, a diode is a two-terminal component, almost always one that has electrical properties which vary depending on the direction of flow of charge...


The most familiar example is a voiceband modem that turns the digital 1s and 0s of a personal computer into sounds that can be transmitted over the telephone lines of Plain Old Telephone Systems (POTS), and once received on the other side, converts those 1s and 0s back into a form used by a USB, Serial, or Network connection. Modems are generally classified by the amount of data they can send in a given time, normally measured in bits per second, or "bps". They can also be classified by Baud, the number of times the modem changes its signal state per second. The binary numeral system, or base-2 number system, is a numeral system that represents numeric values using two symbols, usually 0 and 1. ... A telephone line (or just line) is a single-user circuit on a telephone communications system. ... Plain old telephone service, or POTS, are the services available from analogue telephones prior to the introduction of electronic telephone exchanges into the public switched telephone network. ... In telecommunications and computing, bit rate (sometimes written bitrate) is the frequency at which bits are passing a given (physical or metaphorical) point. It is quantified using the bit per second (bit/s) unit. ... For the town in France, see Baud, Morbihan. ...


Baud is NOT the modem's speed. The baud rate varies, depending on the modulation technique used. Original Bell 103 modems used a modulation technique that saw a change in state 300 times per second. They transmitted 1 bit for every baud, and so a 300 bit/s modem was also a 300-baud modem. However, casual computerists confused the two. A 300 bit/s modem is the only modem whose bit rate matches the baud rate. A 2400 bit/s modem changes state 600 times per second, but due to the fact that it transmits 4 bits for each baud, 2400 bits are transmitted by 600 baud, or changes in states.


Faster modems are used by Internet users every day, notably cable modems and ADSL modems. In telecommunications, "radio modems" transmit repeating frames of data at very high data rates over microwave radio links. Some microwave modems transmit more than a hundred million bits per second. Optical modems transmit data over optical fibers. Most intercontinental data links now use optical modems transmitting over undersea optical fibers. Optical modems routinely have data rates in excess of a billion (1x109) bits per second. One kilobit per second (kbit/s or kb/s or kbps) as used in this article means 1000 bits per second and not 1024 bits per second. For example, a 56k modem can transfer data at up to 56,000 bits per second over the phone line. An outdated model of the Motorola Surfboard cable modem A cable modem is a type of modem that provides access to a data signal sent over the cable television infrastructure. ... Westell Model 6100 ADSL modem An asymmetric digital subscriber line transceiver, also known as an ADSL modem or DSL modem, is a device used to connect a single computer to a DSL phone line, in order to use an ADSL service. ... Telecommunication involves the transmission of signals over a distance for the purpose of communication. ... In telecommunications and computer science, serial communications is the process of sending data one bit at one time, sequentially, over a communications channel or computer bus. ... This article is about the type of Electromagnetic radiation. ... In telecommunications wavelength division multiplexing (WDM) is a technology which multiplexes several optical carrier signals on a single optical fibre by using different wavelengths (colours) of laser light to carry different signals. ... Optical fibers An optical fiber (or fibre) is a glass or plastic fiber designed to guide light along its length. ... A cross-section of a submarine communications cable. ... “KBPS” redirects here. ...

Contents

In computing and telecommunications, the transport layer is the second highest layer in the four and five layer TCP/IP reference models, where it responds to service requests from the application layer and issues service requests to the Internet layer. ... The Transmission Control Protocol (TCP) is one of the core protocols of the Internet protocol suite. ... User Datagram Protocol (UDP) is one of the core protocols of the Internet protocol suite. ... The Datagram Congestion Control Protocol (DCCP) is a message-oriented transport layer protocol that is currently under development in the IETF. Applications that might make use of DCCP include those with timingconstraints on the delivery of data such that reliable in-order delivery, when combined with congestion control, is likely... In the field of computer networking, the IETF Signaling Transport (SIGTRAN) working group defined the Stream Control Transmission Protocol (SCTP) as a transport layer protocol in 2000. ... The Resource ReSerVation Protocol (RSVP), described in RFC 2205, is a Transport layer protocol designed to reserve resources across a network for an integrated services Internet. ... Network congestion avoidance is a process used in computer networks to avoid congestion. ... The network layer is third layer out of seven in OSI model and it is the third layer out of five in TCP/IP model. ... The Internet Protocol (IP) is a data-oriented protocol used for communicating data across a packet-switched internetwork. ... Internet Protocol version 4 (IPv4) is the fourth iteration of the Internet Protocol (IP) and it is the first version of the protocol to be widely deployed. ... Internet Protocol version 6 (IPv6) is a network layer for packet-switched internetworks. ... The Open Shortest Path First (OSPF) protocol is a hierarchical interior gateway protocol (IGP) for routing in Internet Protocol, using a link-state in the individual areas that make up the hierarchy. ... Is Is is Yeah Yeah Yeahs third EP, to be released on July 24, 2007. ... IPsec (IP security) is a suite of protocols for securing Internet Protocol (IP) communications by authenticating and/or encrypting each IP packet in a data stream. ... In computer networking, the Address Resolution Protocol (ARP) is the standard method for finding a hosts hardware address when only its network layer address is known. ... Reverse Address Resolution Protocol (RARP) is a network layer protocol used to obtain an IP address for a given hardware address (such as an Ethernet address). ... This article is chiefly about the Routing Information Protocol (RIP) for the Internet Protocol, but also discusses some other routing information protocols. ... The Internet Control Message Protocol (ICMP) is one of the core protocols of the Internet protocol suite. ... The ICMP for IPv6 (Internet Control Message Protocol Version 6) is an integral part of the IPv6 architecture and must be completely supported by all IPv6 implementations. ... The Internet Group Management Protocol (IGMP) is a communications protocol used to manage the membership of Internet Protocol multicast groups. ... The Border Gateway Protocol (BGP) is the core routing protocol of the Internet. ... The data link layer is layer two of the seven-layer OSI model as well as of the five-layer TCP/IP reference model. ... IEEE 802. ... The IEEE 802. ... Wi-Fi (IPA: ) is the common name for a popular wireless technology used in home networks, mobile phones, video games and more. ... Official WiMax logo WiMAX, the Worldwide Interoperability for Microwave Access, is a telecommunications technology aimed at providing wireless data over long distances in a variety of ways, from point-to-point links to full mobile cellular type access. ... Asynchronous Transfer Mode (ATM) is a cell relay, packet switching network and data link layer protocol which encodes data traffic into small (53 bytes; 48 bytes of data and 5 bytes of header information) fixed-sized cells. ... Dynamic synchronous Transfer Mode , or DTM for short, is a network protocol. ... Token-Ring local area network (LAN) technology was developed and promoted by IBM in the early 1980s and standardised as IEEE 802. ... Ethernet is a large, diverse family of frame-based computer networking technologies that operate at many speeds for local area networks (LANs). ... In computer networking, fiber-distributed data interface (FDDI) is a standard for data transmission in a local area network that can extend in range up to 200 km (124 miles). ... In the context of computer networking, frame relay consists of an efficient data transmission technique used to send digital information quickly and cheaply. ... General Packet Radio Service (GPRS) is a Mobile Data Service available to users of Global System for Mobile Communications (GSM) and IS-136 mobile phones. ... Evolution-Data Optimized or Evolution-Data only, abbreviated as EV-DO or EVDO and often EV, is one telecommunications standard for the wireless transmission of data through radio signals, typically for broadband Internet access. ... High-Speed Packet Access (HSPA) is a collection of mobile telephony protocols that extend and improve the performance of existing UMTS protocols. ... High-Level Data Link Control (HDLC) is a bit-oriented synchronous data link layer protocol developed by the International Organization for Standardization (ISO). ... In computing, the Point-to-Point Protocol, or PPP, is commonly used to establish a direct connection between two nodes. ... The Point-to-Point Tunneling Protocol (PPTP) is a method for implementing virtual private networks. ... In computer networking, the Layer 2 Tunneling Protocol (L2TP) is a tunneling protocol used to support virtual private networks (VPNs). ... ISDN redirects here. ... ARCNET (also CamelCased as ARCnet, an acronym from Attached Resource Computer NETwork) is a local area network (LAN) protocol, similar in purpose to Ethernet or Token Ring. ... Link Layer Topology Discovery (LLTD) is a licensed data link layer protocol for network topology discovery and quality of service diagnostics, developed by Microsoft as part of their Windows Rally set of technologies. ... This article does not cite any references or sources. ... The Ethernet physical layer is the physical layer component of the Ethernet standard. ... RS-232 (also referred to as EIA RS-232C or V.24) is a standard for serial binary data interchange between a DTE (Data terminal equipment) and a DCE (Data communication equipment). ... Synchronous optical networking (SONET) and Synchronous Digital Hierarchy (SDH), are two closely related multiplexing protocols for transferring multiple digital bit streams using lasers or light-emitting diodes (LEDs) over the same optical fiber. ... There are very few or no other articles that link to this one. ... Optical fibers An optical fiber (or fibre) is a glass or plastic fiber designed to guide light along its length. ... Coaxial Cable For the weapon, see coaxial weapon. ... 25 Pair Color Code Chart 10BASE-T UTP Cable Twisted pair cabling is a common form of wiring in which two conductors are wound around each other for the purposes of cancelling out electromagnetic interference known as crosstalk. ...

History

News wire services in the 1920s used multiplex equipment that met the definition, but the modem function was incidental to the multiplexing function, so they are not commonly included in the history of modems. George Stibitz connected a New Hampshire teletype to a computer in New York City by phone lines in 1940. Modems in the United States were part of the SAGE air-defense system in the 1950s, connecting terminals at various airbases, radar sites, and command-and-control centers to the SAGE director centers scattered around the U.S. and Canada. SAGE ran on dedicated communications lines, but the devices at each end were otherwise similar in concept to today's modems. Definition A news agency is an organization of journalists established to supply news reports to organizations in the news trade: newspapers, magazines, and radio and television broadcasters. ... In telecommunications, multiplexing (also muxing or MUXing) is the combining of two or more information channels onto a common transmission medium using hardware called a multiplexer or (MUX). ... George Stibitz George Robert Stibitz (April 20, 1904 – January 31, 1995) is internationally recognized as a father of the modern digital computer. ... A teleprinter (teletypewriter, teletype or TTY) is a now largely obsolete electro-mechanical typewriter which can be used to communicate typed messages from point to point through a simple electrical communications channel, often just a pair of wires. ... SAGE Sector Control Room. ...


A few years later, a chance meeting between the CEO of American Airlines and a regional manager of IBM led to development of a "mini-SAGE" as an automated airline ticketing system. The terminals were at ticketing offices, tied to a central computer that managed availability and scheduling. The system, known as SABRE, is the ancestor of today's Sabre system. Chief Executive redirects here. ... American Airlines, Inc. ... Sabre Logo Sabre is a computer reservations system/global distribution system (GDS) used by airlines, railways, hotels, travel agents and other travel companies. ...


AT&T monopoly in the United States

For many years, AT&T maintained a monopoly in the United States on the use of its phone lines, allowing only AT&T-supplied devices to be attached to its network. For the growing group of computer users, AT&T introduced two digital sub-sets in 1958. One is the wideband device shown in the picture to the right. The other was a low-speed modem, which ran at 200 baud. This article is about the current AT&T. For the 1885-2005 company, see American Telephone & Telegraph. ... For the town in France, see Baud, Morbihan. ...

Legacy modem for leased line operation.
Legacy modem for leased line operation.

In the summer of 1960, the name Data-Phone was introduced to replace the earlier term digital subset. The 202 Data-Phone was a half-duplex asynchronous service that was marketed extensively in late 1960. In 1962, the 201A and 201B Data-Phones were introduced. They were synchronous modems using two-bit-per-baud phase-shift keying (PSK). The 201A operated half-duplex at 2000 bit/s over normal phone lines, while the 201B provided full duplex 2400 bit/s service on four-wire leased lines, the send and receive channels running on their own set of two wires each. Image File history File links Size of this preview: 800 × 582 pixelsFull resolution (2813 × 2047 pixel, file size: 1. ... Image File history File links Size of this preview: 800 × 582 pixelsFull resolution (2813 × 2047 pixel, file size: 1. ... In telecommunications, duplex means two-way when referring to communications channels. ... In telecommunication, the term phase-shift keying (PSK) has the following meanings: 1. ... Duplex is the having of two principal elements or parts. ...


The famous 103A was also introduced in 1962. It provided full-duplex service at up to 300 baud over normal phone lines. Frequency-shift keying (FSK) was used with the call originator transmitting at 1070 or 1270 Hz and the answering modem transmitting at 2025 or 2225 Hz. The readily available 103A2 gave an important boost to the use of remote low-speed terminals such as the KSR33, the ASR33, and the IBM 2741. AT&T reduced modem costs by introducing the originate-only 113D and the answer-only 113B/C modems. Frequency-shift keying (FSK) is frequency modulation in which the modulating signal shifts the output frequency between predetermined values. ... This article is about the SI unit of frequency. ... Introduced about 1963, Teletype Corporations ASR33 was a very popular model of teleprinter. ... IBM logo The 2741 was a low-speed dumb terminal introduced in 1965. ...


The Carterfone decision

The Novation CAT acoustically coupled modem
The Novation CAT acoustically coupled modem

Before 1968, AT&T maintained a monopoly on what devices could be electrically connected to its phone lines. This led to a market for 103A-compatible modems that were mechanically connected to the phone, through the handset, known as acoustically coupled modems. Particularly common models from the 1970s were the Novation CAT (shown in the image) and the Anderson-Jacobson, spun off from an in-house project at the Lawrence Livermore National Laboratory. Download high resolution version (1542x1178, 292 KB)This photo of an accousticly coupled modem was taken by user Lorax and dedicated to the Public Domain This image has been released into the public domain by the copyright holder, its copyright has expired, or it is ineligible for copyright. ... Download high resolution version (1542x1178, 292 KB)This photo of an accousticly coupled modem was taken by user Lorax and dedicated to the Public Domain This image has been released into the public domain by the copyright holder, its copyright has expired, or it is ineligible for copyright. ... The Novation CAT acoustically coupled modem In telecommunications, the term acoustic coupler has the following meanings: An interface device for coupling electrical signals by acoustical means--usually into and out of a telephone instrument. ... The original Novation CAT Novation was an early modem manufacturer, whos CAT series were popular in the early home computer market in the late 1970s, notably on the Apple II. The Hayes Smartmodem 300, introduced in 1981, killed off Novation and many other early modem companies over the next... Aerial view of the lab and surrounding area, facing NW. The Lawrence Livermore National Laboratory (LLNL) in Livermore, California is a United States Department of Energy (DOE) national laboratory, managed and operated by Lawrence Livermore National Security, LLC (LLNS), a limited liability consortium comprised of Bechtel National, the University of...


Hush-a-Phone v. FCC was a seminal ruling in United States telecommunications law decided by the DC Circuit Court of Appeals on November 8, 1956. The District Court found that it was within the FCC's authority to regulate the terms of use of AT&T's equipment. Subsequently, the FCC examiner found that as long as the device was physically attached it would not threaten to degenerate the system. Later, in the Carterfone decision, the FCC passed a rule setting stringent AT&T-designed tests for electronically coupling a device to the phone lines. AT&T made these tests complex and expensive, so acoustically coupled modems remained common into the early 1980s. Hush-a-Phone v. ... Telecommunication involves the transmission of signals over a distance for the purpose of communication. ... The United States Court of Appeals for the District of Columbia Circuit, known informally as the D.C. Circuit, is the federal appellate court for the U.S. District Court for the District of Columbia. ... is the 312th day of the year (313th in leap years) in the Gregorian calendar. ... A car from 1956 Year 1956 (MCMLVI) was a leap year starting on Sunday (link will display full calendar) of the Gregorian calendar. ... This is a device which was invented by Thomas Carter. ...


In December 1972, Vadic introduced the VA3400. This device was remarkable because it provided full duplex operation at 1200 bit/s over the dial network, using methods similar to those of the 103A in that it used different frequency bands for transmit and receive. In November 1976, AT&T introduced the 212A modem to compete with Vadic. It was similar in design to Vadic's model, but used the lower frequency set for transmission. It was also possible to use the 212A with a 103A modem at 300 bit/s. According to Vadic, the change in frequency assignments made the 212 intentionally incompatible with acoustic coupling, thereby locking out many potential modem manufacturers. In 1977, Vadic responded with the VA3467 triple modem, an answer-only modem sold to computer center operators that supported Vadic's 1200-bit/s mode, AT&T's 212A mode, and 103A operation.


The Smartmodem and the rise of BBSes

US Robotics Sportster 14,400 Fax modem (1994)
US Robotics Sportster 14,400 Fax modem (1994)

The next major advance in modems was the Smartmodem, introduced in 1981 by Hayes Communications. The Smartmodem was an otherwise standard 103A 300-bit/s modem, but was attached to a small controller that let the computer send commands to it and enable it to operate the phone line. The command set included instructions for picking up and hanging up the phone, dialing numbers, and answering calls. The basic Hayes command set remains the basis for computer control of most modern modems. U.S. Robotics (popularly nicknamed USR), based in Schaumburg, Illinois and founded in 1976, is a company that makes computer modems and related technologies. ... Hayes Communications was a U.S.-based manufacturer of modems. ... This article or section does not cite its references or sources. ...


Prior to the Hayes Smartmodem, modems almost universally required a two-step process to activate a connection: first, the user had to manually dial the remote number on a standard phone handset, and then secondly, plug the handset into an acoustic coupler. Hardware add-ons, known simply as dialers, were used in special circumstances, and generally operated by emulating someone dialing a handset.


With the Smartmodem, the computer could dial the phone directly by sending the modem a command, thus eliminating the need for an associated phone for dialing and the need for an acoustic coupler. The Smartmodem instead plugged directly into the phone line. This greatly simplified setup and operation. Terminal programs that maintained lists of phone numbers and sent the dialing commands became common.


The Smartmodem and its clones also aided the spread of bulletin-board systems (BBSs). Modems had previously been typically either the call-only, acoustically coupled models used on the client side, or the much more expensive, answer-only models used on the server side. The Smartmodem could operate in either mode depending on the commands sent from the computer. There was now a low-cost server-side modem on the market, and the BBSs flourished. Ward Christensen and the computer that ran the first public Bulletin Board Systems, CBBS A Bulletin board system, or BBS, is a computer system running software that allows users to dial into the system over a phone line (or Telnet) and, using a terminal program, perform functions such as downloading...


Softmodem (dumb modem)

Main article: Softmodem
A PCI Winmodem/Softmodem (on the left) next to a traditional ISA modem (on the right). Notice the less complex circuitry of the modem on the left.
A PCI Winmodem/Softmodem (on the left) next to a traditional ISA modem (on the right). Notice the less complex circuitry of the modem on the left.

A Winmodem or Softmodem is a stripped-down modem that replaces tasks traditionally handled in hardware with software. In this case the modem is a simple digital signal processor designed to create sounds, or voltage variations, on the telephone line. Softmodems are cheaper than traditional modems, since they have fewer hardware components. One downside is that the software generating the modem tones is not simple, and the performance of the computer as a whole often suffers when it is being used. For online gaming this can be a real concern. Another problem is lack of portability such that other OSes (such as Linux) may not have an equivalent driver to operate the modem. A Winmodem might not work with a later version of Microsoft Windows, if its driver turns out to be incompatible with that later version of the operating system. A PCI Winmodem/Softmodem (on the left) next to a traditional ISA modem (on the right). ... Image File history File linksMetadata Download high resolution version (2592x1944, 1557 KB) Summary An image I took of a 56k (v. ... Image File history File linksMetadata Download high resolution version (2592x1944, 1557 KB) Summary An image I took of a 56k (v. ... For other uses, see Hardware (disambiguation). ... Computer software (or simply software) refers to one or more computer programs and data held in the storage of a computer for some purpose. ... This article is about operating systems that use the Linux kernel. ...


Apple's GeoPort modems from the second half of the 1990s were similar. Although a clever idea in theory, enabling the creation of more-powerful telephony applications, in practice the only programs created were simple answering-machine and fax software, hardly more advanced than their physical-world counterparts, and certainly more error-prone and cumbersome. The software was finicky and ate up significant processor time, and no longer functions in current operating system versions. Apple Inc. ... GeoPort was a serial data system used on some models of the Apple Macintosh. ...


Almost all modern modems also do double-duty as a fax machine as well. Digital faxes, introduced in the 1980s, are simply a particular image format sent over a high-speed (9600/1200 bit/s) modem. Software running on the host computer can convert any image into fax-format, which can then be sent using the modem. Such software was at one time an add-on, but since has become largely universal. For other uses, see Fax (disambiguation). ... See also Category:Graphics file formats Here is a summary of the most common graphics file formats: Some file formats, e. ...


Narrowband/phone-line dialup modems

28.8 kbit/s serial-port modem from Motorola
28.8 kbit/s serial-port modem from Motorola

A standard modem of today contains two functional parts: an analog section for generating the signals and operating the phone, and a digital section for setup and control. This functionality is actually incorporated into a single chip, but the division remains in theory. In operation the modem can be in one of two "modes", data mode in which data is sent to and from the computer over the phone lines, and command mode in which the modem listens to the data from the computer for commands, and carries them out. A typical session consists of powering up the modem (often inside the computer itself) which automatically assumes command mode, then sending it the command for dialing a number. After the connection is established to the remote modem, the modem automatically goes into data mode, and the user can send and receive data. When the user is finished, the escape sequence, "+++" followed by a pause of about a second, is sent to the modem to return it to command mode, and the command ATH to hang up the phone is sent. Image File history File links Motorola_modem_28k. ... Image File history File links Motorola_modem_28k. ... A male DE-9 connector used for a serial port on a PC style computer. ... Motorola Inc. ... To meet Wikipedias quality standards, this article or section may require cleanup. ...


The commands themselves are typically from the Hayes command set, although that term is somewhat misleading. The original Hayes commands were useful for 300 bit/s operation only, and then extended for their 1200 bit/s modems. Faster speeds required new commands, leading to a proliferation of command sets in the early 1990s. Things became considerably more standardized in the second half of the 1990s, when most modems were built from one of a very small number of "chip sets". We call this the Hayes command set even today, although it has three or four times the numbers of commands as the actual standard. This article or section does not cite its references or sources. ...


Increasing speeds (V.21 V.22 V.22bis)

A 2400 bit/s modem for a laptop.
A 2400 bit/s modem for a laptop.

The 300 bit/s modems used frequency-shift keying to send data. In this system the stream of 1s and 0s in computer data is translated into sounds which can be easily sent on the phone lines. In the Bell 103 system the originating modem sends 0s by playing a 1070 Hz tone, and 1s at 1270 Hz, with the answering modem putting its 0s on 2025 Hz and 1s on 2225 Hz. These frequencies were chosen carefully, they are in the range that suffer minimum distortion on the phone system, and also are not harmonics of each other. Image File history File linksMetadata Download high resolution version (1572x1051, 515 KB) Summary A 2400 Baud modem for a laptop. ... Image File history File linksMetadata Download high resolution version (1572x1051, 515 KB) Summary A 2400 Baud modem for a laptop. ... It has been suggested that this article or section be merged with audio frequency-shift keying. ... This article is about the components of sound. ...


In the 1200 bit/s and faster systems, phase-shift keying was used. In this system the two tones for any one side of the connection are sent at the similar frequencies as in the 300 bit/s systems, but slightly out of phase. By comparing the phase of the two signals, 1s and 0s could be pulled back out, for instance if the signals were 90 degrees out of phase, this represented two digits, "1,0", at 180 degrees it was "1,1". In this way each cycle of the signal represents two digits instead of one. 1200 bit/s modems were, in effect, 600 symbols per second modems (600 baud modems) with 2 bits per symbol. Phase-shift keying (PSK) is a digital modulation scheme that conveys data by changing, or modulating, the phase of a reference signal (the carrier wave). ...


Voiceband modems generally remained at 300 and 1200 bit/s (V.21 and V.22) into the mid 1980s. A V.22bis 2400-bit/s system similar in concept to the 1200-bit/s Bell 212 signalling was introduced in the U.S., and a slightly different one in Europe. By the late 1980s, most modems could support all of these standards and 2400-bit/s operation was becoming common. V.21 is an ITU-T recommendation for full-duplex communication between two analogue dial-up modems using audio frequency-shift keying modulation at 300 bauds to carry digital data at 300 bit/s. ... The V-22 Osprey is a joint service, multi-mission aircraft with vertical take-off and landing (VTOL) capability. ... V.22 bis is an ITU-T recommendation extending V.22 with a faster rate using QAM modulation at 600 bauds to carry digital data at 2400 or 1200 bit/s. ...


For more information on baud rates versus bitrates, see the companion article List of device bandwidths. This is a list of device bandwidths: the channel capacity (or, more informally, bandwidth) of some computer devices employing methods of data transport is quantified in units of kilobits per second (kbit/s), megabits per second (Mbit/s), or gigabits per second (Gbit/s) as appropriate. ...


Increasing speeds (one-way proprietary standards)

Many other standards were also introduced for special purposes, commonly using a high-speed channel for receiving, and a lower-speed channel for sending. One typical example was used in the French Minitel system, in which the user's terminals spent the majority of their time receiving information. The modem in the Minitel terminal thus operated at 1200 bit/s for reception, and 75 bit/s for sending commands back to the servers. Minitel 1. ... In information technology, a server is an application or device that performs services for connected clients as part of a client-server architecture. ...


Three U.S. companies became famous for high-speed versions of the same concept. Telebit introduced its Trailblazer modem in 1984, which used a large number of 36 bit/s channels to send data one-way at rates up to 18,400 bit/s. A single additional channel in the reverse direction allowed the two modems to communicate how much data was waiting at either end of the link, and the modems could change direction on the fly. The Trailblazer modems also supported a feature that allowed them to "spoof" the UUCP "g" protocol, commonly used on Unix systems to send e-mail, and thereby speed UUCP up by a tremendous amount. Trailblazers thus became extremely common on Unix systems, and maintained their dominance in this market well into the 1990s. Telebit, a modem manufacturer, is most notable for the Trailblazer variety modems. ... In relation to computer technology, on the fly describes activities that develop or occur dynamically rather than as the result of something that is statically predefined. ... UUCP stands for Unix to Unix CoPy. ... Filiation of Unix and Unix-like systems Unix (officially trademarked as UNIX®, sometimes also written as or ® with small caps) is a computer operating system originally developed in 1969 by a group of AT&T employees at Bell Labs including Ken Thompson, Dennis Ritchie and Douglas McIlroy. ... Wikipedia does not yet have an article with this exact name. ...


U.S. Robotics (USR) introduced a similar system, known as HST, although this supplied only 9600 bit/s (in early versions at least) and provided for a larger backchannel. Rather than offer spoofing, USR instead created a large market among Fidonet users by offering its modems to BBS sysops at a much lower price, resulting in sales to end users who wanted faster file transfers. Hayes was forced to compete, and introduced its own 9600-bit/s standard, Express 96 (also known as "Ping-Pong"), which was generally similar to Telebit's PEP. Hayes, however, offered neither protocol spoofing nor sysop discounts, and its high-speed modems remained rare. U.S. Robotics (popularly referred to by its acronym USR) is a company that makes computer modems and related technologies. ... The FidoNet logo FidoNet is a worldwide computer network that is used for communication between bulletin board systems. ... SysOp (pronounced /ˈsɪs. ...


4800 and 9600 (V.27ter, V.32)

Echo cancellation was the next major advance in modem design. Local telephone lines use the same wires to send and receive, which results in a small amount of the outgoing signal bouncing back. This signal can confuse the modem. Is the signal it is "hearing" a data transmission from the remote modem, or its own transmission bouncing back? This was why earlier modems split the signal frequencies into answer and originate; each modem simply didn't listen to its own transmitting frequencies. Even with improvements to the phone system allowing higher speeds, this splitting of available phone signal bandwidth still imposed a half-speed limit on modems. The term echo cancellation is used in telephony to describe the process of removing echo from a voice communication in order to improve voice quality on a telephone call. ...


Echo cancellation got around this problem. Measuring the echo delays and magnitudes allowed the modem to tell if the received signal was from itself or the remote modem, and create an equal and opposite signal to cancel its own. Modems were then able to send at "full speed" in both directions at the same time, leading to the development of 4800 and 9600 bit/s modems.


Increases in speed have used increasingly complicated communications theory. 1200 and 2400 bit/s modems used the phase shift key (PSK) concept. This could transmit two or three bits per symbol. The next major advance encoded four bits into a combination of amplitude and phase, known as Quadrature Amplitude Modulation (QAM). Best visualized as a constellation diagram, the bits are mapped onto points on a graph with the x (real) and y (quadrature) coordinates transmitted over a single carrier. “QAM” redirects here. ... A constellation diagram is a representation of a digital modulation scheme in the complex plane. ...


The new V.27ter and V.32 standards were able to transmit 4 bits per symbol, at a rate of 1200 or 2400 baud, giving an effective bit rate of 4800 or 9600 bits per second. The carrier frequency was 1650 Hz. For many years, most engineers considered this rate to be the limit of data communications over telephone networks.


Error correction and compression

Operations at these speeds pushed the limits of the phone lines, resulting in high error rates. This led to the introduction of error-correction systems built into the modems, made most famous with Microcom's MNP systems. A string of MNP standards came out in the 1980s, each increasing the effective data rate by minimizing overhead, from about 75% theoretical maximum in MNP 1, to 95% in MNP 4. The new method called MNP 5 took this a step further, adding data compression to the system, thereby increasing the data rate above the modem's rating. Generally the user could expect an MNP5 modem to transfer at about 130% the normal data rate of the modem. MNP was later "opened" and became popular on a series of 2400-bit/s modems, and ultimately led to the development of V.42 and V.42bis ITU standards. V.42 and V.42bis were non-compatible with MNP but were similar in concept: Error correction and compression. It has been suggested that this article or section be merged with Forward error correction. ... Microcom Systems was a major modem vendor during the 1980s, although they were never as popular as the big three, Hayes, U.S. Robotics and Telebit. ... The MNP (Microcom Networking Protocol) family of error-correcting protocols were commonly used on early high-speed (2400 bps and higher) modems. ... Source coding redirects here. ... V. 42 is an error correction protocol promoted by the ITU-T, a technical standards group within the United Nations]. Its function is to allow the receiver to immediately request re-transmission of any lost data packets. ... V.42bis is an adaptive data compression standard in common use nowadays. ...


Another common feature of these high-speed modems was the concept of fallback, allowing them to talk to less-capable modems. During the call initiation the modem would play a series of signals into the line and wait for the remote modem to "answer" them. They would start at high speeds and progressively get slower and slower until they heard an answer. Thus, two USR modems would be able to connect at 9600 bit/s, but, when a user with a 2400-bit/s modem called in, the USR would "fall back" to the common 2400-bit/s speed. This would also happen if a V.32 modem and a HST modem were connected. Because they used a different standard at 9600 bit/s, they would fall back to their highest commonly supported standard at 2400 bit/s. The same applies to V.32bis and 14400 bit/s HST modem, which would still be able to communicate with each other at only 2400 bit/s. Fall back is a feature of a modem protocol in data communication whereby two communicating modems which experience data corruption (due to line noise, for example) can renegotiate with each other to use a lower-speed connection. ...


Breaking the 9.6k barrier

In 1980 Gottfried Ungerboeck from IBM Zurich Research Laboratory applied powerful channel coding techniques to search for new ways to increase the speed of modems. His results were astonishing but only conveyed to a few colleagues[1]. Finally in 1982, he agreed to publish what is now a landmark paper in the theory of information coding.[citation needed] By applying powerful parity check coding to the bits in each symbol, and mapping the encoded bits into a two dimensional "diamond pattern", Ungerboeck showed that it was possible to increase the speed by a factor of two with the same error rate. The new technique was called "mapping by set partitions" (now known as trellis modulation). This new view was an extension of the "penny packing" problem[clarify] and the related and more general problem of how to pack points into an N-dimension sphere such that they are far away from their neighbors. The greater two bit sequences are from one another, the easier it is to correct minor errors. Gottfried Ungerboeck received the engineering degree in telecommunications in 1964 and the Ph. ... IBM Research, a subsidiary of IBM, has existed since 1945 and currently consists of eight locations throughout the world and hundreds of projects. ... In digital telecommunications, channel coding is a pre-transmission mapping applied to a digital signal or data file, usually designed to make error-correction possible. ... The introduction to this article provides insufficient context for those unfamiliar with the subject matter. ...


The industry was galvanized into new research and development. More powerful coding techniques were developed, commercial firms rolled out new product lines, and the standards organizations rapidly adopted to new technology. The "tipping point" occurred with the introduction of the SupraFax 14400 in 1991. Rockwell had introduced a new chipset supporting not only V.32 and MNP, but the newer 14,400 bit/s V.32bis and the higher-compression V.42bis as well, and even included 9600 bit/s fax capability. Supra, then known primarily for their hard drive systems, used this chip set to build a low-priced 14,400 bit/s modem which cost the same as a 2400 bit/s modem from a year or two earlier (about US$300). The product was a runaway best-seller, and it was months before the company could keep up with demand. Rockwell International was the ultimate incarnation of a series of companies under the sphere of influence of Willard Rockwell, who had made his fortune after the invention and successful launch of a new bearing system for truck axles in 1919. ... V.32bis is an ITU-T recommendation for a modem, allowing up to 14. ... V.42bis is an adaptive data compression standard in common use nowadays. ... For other uses, see Fax (disambiguation). ... Typical hard drives of the mid-1990s. ...


V.32bis was so successful that the older high-speed standards had little to recommend them. USR fought back with a 16,800 bit/s version of HST, while AT&T introduced a one-off 19,200 bit/s method they referred to as V.32ter (also known as V.32 terbo), but neither non-standard modem sold well.


V.34 / 28.8k and 33.8k
An ISA modem manufactured to conform to the V.34 protocol.
An ISA modem manufactured to conform to the V.34 protocol.

Any interest in these systems was destroyed during the lengthy introduction of the 28,800 bit/s V.34 standard. While waiting, several companies decided to "jump the gun" and introduced modems they referred to as "V.FAST". In order to guarantee compatibility with V.34 modems once the standard was ratified (1994), the manufacturers were forced to use more "flexible" parts, generally a DSP and microcontroller, as opposed to purpose-designed "modem chips". Image File history File linksMetadata Download high resolution version (1944x2592, 1595 KB) Summary Image taken by me of an ISA modem, v. ... Image File history File linksMetadata Download high resolution version (1944x2592, 1595 KB) Summary Image taken by me of an ISA modem, v. ... V.34 is: The communication protocol from ITU for 28. ... The abbreviation DSP can refer to: // Digital signal processing, the study of signals in a digital representation and their processing methods Digital signal processor, a specialized microprocessor designed specifically for digital signal processing Dylan Server Pages, a web template engine using the Dylan language Delivery Service Partner, a type of... It has been suggested that this article or section be merged with embedded microprocessor. ...


Today the ITU standard V.34 represents the culmination of the joint efforts. It employs the most powerful coding techniques including channel encoding and shape encoding. From the mere 4 bits per symbol (9.6 kbit/s), the new standards used the functional equivalent of 6 to 10 bits per symbol, plus increasing baud rates from 2400 to 3429, to create 14.4, 28.8, and 33.8 kbit/s modems. (See Tables 8 and 10 of the specification; maximum speed listed as "33 800".) This rate is near the theoretical Shannon limit. When calculated, the Shannon capacity of a narrowband line is Bandwidth * log2(1 + Pu / Pn), with Pu / Pn the signal-to-noise ratio. Narrowband phone lines have a bandwidth from 300-3100 Hz, so using Pu / Pn = 100,000: capacity is approximately 35 kbit/s. In information theory, the Shannon-Hartley theorem states the maximum amount of error-free digital data (that is, information) that can be transmitted over a communication link with a specified bandwidth in the presence of noise interference. ...


Without the discovery and eventual application of trellis modulation, maximum telephone rates would have been limited to 3429 baud * 4 bits/symbol == approximately 14 kilobits per second using traditional QAM.[citation needed]


Using digital lines and PCM (V.90/92)

In the late 1990s Rockwell and U.S. Robotics introduced new technology based upon the digital transmission used in modern telephony networks. The standard digital transmission in modern networks is 64 kbit/s but some networks use a part of the bandwidth for remote office signaling (eg to hang up the phone), limiting the effective rate to 56 kbit/s DS0. This new technology was adopted into ITU standards V.90 and is common in modern computers. The 56 kbit/s rate is only possible from the central office to the user site (downlink) and in the United States, government regulation limits the maximum power output to only 53.3 kbit/s. The uplink (from the user to the central office) still uses V.34 technology at 33.6k. In T-carrier systems Digital signal 0 (DS0) is a basic digital signaling rate of 64 kb/s, corresponding to the capacity of one voice-frequency-equivalent channel. ...


Later in V.92, the digital PCM technique was applied to increase the upload speed to a maximum of 48 kbit/s, but at the expense of download rates. For example a 48 kbit/s upstream rate would reduce the downstream as low as 40 kbit/s, due to echo on the telephone line. To avoid this problem, V.92 modems offer the option to turn off the digital upstream and instead use a 33.6 kbit/s analog connection, in order to maintain a high digital downstream of 50 kbit/s or higher. (See November and October 2000 update at http://www.modemsite.com/56k/v92s.asp ) V.92 also adds two other features. The first is the ability for users who have call waiting to put their dial-up Internet connection on hold for extended periods of time while they answer a call. The second feature is the ability to "quick connect" to one's ISP. This is achieved by remembering the analog and digital characteristics of the telephone line, and using this saved information to reconnect at a fast pace. V.92 is an ITU-T modem standard allowing near 56 kbit/s download and 48 kbit/s upload rates first presented in August 1999. ... PCM is an initialism which can have different meanings: Phase Change Material Pulse-code modulation, a way to digitally encode signals representing sound and their video counterparts Potential Cancer Marker Communist Party of Mexico Plug Compatible Manufacturer Power-train control module, a computer in a car which controls the car... Dial-up access is a form of Internet access via telephone line. ...


Using compression to exceed 56k

Today's V.42, V.42bis and V.44 standards allow the modem to transmit data faster than its basic rate would imply. For instance, a 53.3 kbit/s connection with V.44 can transmit up to 53.3*6 == 320 kbit/s using pure text. However, the compression ratio tends to vary due to noise on the line, or due to the transfer of already-compressed files (ZIP files, JPEG images, MP3 audio, MPEG video). [2] At some points the modem will be sending compressed files at approximately 50 kbit/s, uncompressed files at 160 kbit/s, and pure text at 320 kbit/s, or any value in between. [3] V. 42 is an error correction protocol promoted by the ITU-T, a technical standards group within the United Nations]. Its function is to allow the receiver to immediately request re-transmission of any lost data packets. ... V.42bis is an adaptive data compression standard in common use nowadays. ... V.44 is an adaptive data compression standard incorporated into the v. ...


In such situations a small amount of memory in the modem, a buffer, is used to hold the data while it is being compressed and sent across the phone line, but in order to prevent overflow of the buffer, it sometimes becomes necessary to tell the computer to pause the datastream. This is accomplished through hardware flow control using extra lines on the modem–computer connection. The computer is then set to supply the modem at some higher rate, such as 320 kbit/s, and the modem will tell the computer when to start or stop sending data.


Compression by the ISP

As telephone-based 56k modems began losing popularity, some Internet Service Providers such as Netzero and Juno started using pre-compression to increase the throughput & maintain their customer base. As example, the Netscape ISP uses a compression program that squeezes images, text, and other objects at the server, just prior to sending them across the phone line. The server-side compression operates much more efficiently than the "on-the-fly" compression of V.44-enabled modems. Typically website text is compacted to 4% thus increasing effective throughput to approximately 1300 kbit/s. The accelerator also precompresses Flash executables and images to approximately 30% and 12%, respectively. For the web browser produced by this corporation, see Netscape (web browser). ...


The drawback of this approach is a loss in quality, where the graphics become heavily compacted and smeared, but the speed is dramatically improved such that webpages load in less than 5 seconds, and the user can manually choose to view the uncompressed images at any time. The ISPs employing this approach advertise it as "DSL speeds over regular phone lines" or simply "high speed dialup".


List of dialup speeds

Note that the values given are maximum values, and actual values may be slower under certain conditions (for example, noisy phone lines).[4] For a complete list see the companion article List of device bandwidths. This is a list of device bandwidths: the channel capacity (or, more informally, bandwidth) of some computer devices employing methods of data transport is quantified in units of kilobits per second (kbit/s), megabits per second (Mbit/s), or gigabits per second (Gbit/s) as appropriate. ...

Connection Bitrate
Modem 110 baud 0.1 kbit/s
Modem 300 (300 baud) (Bell 103 or V.21) 0.3 kbit/s
Modem 1200 (600 baud) (Bell 212A or V.22) 1.2 kbit/s
Modem 2400 (600 baud) (V.22bis) 2.4 kbit/s
Modem 2400 (1200 baud) (V.26bis) 2.4 kbit/s
Modem 4800 (1600 baud) (V.27ter) 4.8 kbit/s
Modem 9600 (2400 baud) (V.32) 9.6 kbit/s
Modem 14.4 (2400 baud) (V.32bis) 14.4 kbit/s
Modem 28.8 (3200 baud) (V.34) 28.8 kbit/s
Modem 33.6 (3429 baud) (V.34) 33.8 kbit/s
Modem 56k (8000/3429 baud) (V.90) 56.0/33.6 kbit/s
Modem 56k (8000/8000 baud) (V.92) 56.0/48.0 kbit/s
Bonding Modem (two 56k modems)) (V.92) 112.0/96.0 kbit/s [5]
Hardware compression (variable) (V.90/V.42bis) 56.0-220.0 kbit/s
Hardware compression (variable) (V.92/V.44) 56.0-320.0 kbit/s
Server-side web compression (variable) (Netscape ISP) 100.0-1000.0 kbit/s

In telecommunications and computing, bitrate (sometimes written bit rate, data rate or as a variable Rbit) is the number of bits that are conveyed or processed per unit of time. ... For the town in France, see Baud, Morbihan. ... The Bell 103 modem was the first commercial modem for computers, released by AT&T in 1962. ... V.21 is an ITU-T recommendation for full-duplex communication between two analogue dial-up modems using audio frequency-shift keying modulation at 300 bauds to carry digital data at 300 bit/s. ... The Bell 212A modulation scheme defined a standard method of transmitting full-duplex asynchronous serial data at 1. ... The V-22 Osprey is a joint service, multi-mission aircraft with vertical take-off and landing (VTOL) capability. ... V.22 bis is an ITU-T recommendation extending V.22 with a faster rate using QAM modulation at 600 bauds to carry digital data at 2400 or 1200 bit/s. ... This article or section is in need of attention from an expert on the subject. ... This article or section is in need of attention from an expert on the subject. ... V.32 is an ITU-T recommendation for a modem, allowing bidirectional data transfer at either 9. ... V.32bis is an ITU-T recommendation for a modem, allowing up to 14. ... V.34 is: The communication protocol from ITU for 28. ... V.34 is: The communication protocol from ITU for 28. ... V.90 is an ITU-T recommendation for a modem, allowing 56 kbit/s download and 33. ... V.92 is an ITU-T modem standard allowing near 56 kbit/s download and 48 kbit/s upload rates first presented in August 1999. ... V.92 is an ITU-T modem standard allowing near 56 kbit/s download and 48 kbit/s upload rates first presented in August 1999. ... V.90 is an ITU-T recommendation for a modem, allowing 56 kbit/s download and 33. ... V.42bis is an adaptive data compression standard in common use nowadays. ... V.92 is an ITU-T modem standard allowing near 56 kbit/s download and 48 kbit/s upload rates first presented in August 1999. ... V.44 is an adaptive data compression standard incorporated into the v. ... For the web browser produced by this corporation, see Netscape (web browser). ...

Radio modems

Direct broadcast satellite, WiFi, and mobile phones all use modems to communicate, as do most other wireless services today. Modern telecommunications and data networks also make extensive use of radio modems where long distance data links are required. Such systems are an important part of the PSTN, and are also in common use for high-speed computer network links to outlying areas where fibre is not economical. Direct broadcast satellite (DBS) is a term used to refer to satellite television broadcasts intended for home reception, also referred to as direct-to-home signals. ... Wi-Fi (or Wi-fi, WiFi, Wifi, wifi), short for Wireless Fidelity, is a set of standards for wireless local area networks (WLAN) currently based on the IEEE 802. ... A radio modem is a modem that transmits data through radio waves instead of a fixed pair of wires, such as the POTS network. ... The public switched telephone network (PSTN) is the concatenation of the worlds public circuit-switched telephone networks, in much the same way that the Internet is the concatenation of the worlds public IP-based packet-switched networks. ... This article or section is in need of attention from an expert on the subject. ...


Even where a cable is installed, it is often possible to get better performance or make other parts of the system simpler by using radio frequencies and modulation techniques through a cable. Coaxial cable has a very large bandwidth, however signal attenuation becomes a major problem at high data rates if a digital signal is used. By using a modem, a much larger amount of digital data can be transmitted through a single piece of wire. Digital cable television and cable Internet services use radio frequency modems to provide the increasing bandwidth needs of modern households. Using a modem also allows for frequency-division multiple access to be used, making full-duplex digital communication with many users possible using a single wire. Coaxial Cable For the weapon, see coaxial weapon. ... This article is in need of attention from an expert on the subject. ...


Wireless modems come in a variety of types, bandwidths, and speeds. Wireless modems are often referred to as transparent or smart. They transmit information that is modulated onto a carrier frequency to allow many simultaneous wireless communication links to work simultaneously on different frequencies.


Transparent modems operate in a manner similar to their phone line modem cousins. Typically, they were half duplex, meaning that they could not send and receive data at the same time. Typically transparent modems are polled in a round robin manner to collect small amounts of data from scattered locations that do not have easy access to wired infrastructure. Transparent modems are most commonly used by utility companies for data collection. Duplex is the having of two principal elements or parts. ...


Smart modems come with a media access controller inside which prevents random data from colliding and resends data that is not correctly received. Smart modems typically require more bandwidth than transparent modems, and typically achieve higher data rates. The IEEE 802.11 standard defines a short range modulation scheme that is used on a large scale throughout the world. IEEE 802. ...


WiFi and WiMax

Wireless data modems are used in the WiFi and WiMax standards, operating at microwave frequencies. Mobile phones can be employed as data modems to form a wireless access point connecting a personal computer to The Internet (or some proprietary network). ... Wi-Fi (or Wi-fi, WiFi, Wifi, wifi), short for Wireless Fidelity, is a set of standards for wireless local area networks (WLAN) currently based on the IEEE 802. ... Official WiMax logo WiMAX, the Worldwide Interoperability for Microwave Access, is a telecommunications technology aimed at providing wireless data over long distances in a variety of ways, from point-to-point links to full mobile cellular type access. ... This article is about the type of Electromagnetic radiation. ...


WiFi is principally used in laptops for Internet connections (wireless access point) and wireless application protocol (WAP). Wi-Fi (or Wi-fi, WiFi, Wifi, wifi), short for Wireless Fidelity, is a set of standards for wireless local area networks (WLAN) currently based on the IEEE 802. ... An ultraportable IBM X31 with 12 screen on an IBM T43 Thin & Light laptop with a 14 screen A laptop computer, or simply laptop (also notebook computer, notebook and notepad) is a small mobile computer, typically weighing 3-12 pounds (around 1. ... Planet WAP-4000 Wireless Access Point In computer networking, a wireless access point (WAP or AP) is a device that connects wireless communication devices together to form a wireless network. ... WAP is an open international standard for applications that use wireless communication. ...


Mobile modems & routers

External modems for mobile phone lines (GPRS and UMTS), are also known as datacards and cellular routers. The datacard is a PC card, where a phone card is included, whereas a cellular router may or may not have an external datacard. Most cellular routers do, except for the WAAV CM3 mobile broadband cellular router. General Packet Radio Service (GPRS) is a mobile data service available to users of GSM mobile phones. ... Universal Mobile Telecommunications System (UMTS) is one of the third-generation (3G) mobile phone technologies. ... A radio modem is a modem that transmits data through radio waves instead of a fixed pair of wires, such as the POTS network. ... Cellular routers (sometimes known as 3G Routers) are routers that provide shared Internet access by incorporating a cellular data modem as a WAN interface. ... The PCMCIA is the Personal Computer Memory Card International Association, an industry trade association that creates standards for notebook computer peripheral devices. ... This article is about telephone cards, also called calling cards. ... Cellular routers (sometimes known as 3G Routers) are routers that provide shared Internet access by incorporating a cellular data modem as a WAN interface. ... WAAV (980 AM) is a radio station broadcasting a News/Talk format. ... Cellular routers (sometimes known as 3G Routers) are routers that provide shared Internet access by incorporating a cellular data modem as a WAN interface. ...


Nowadays, there are USB modems with an integrated SIM cardholder (i.e, Huawei E220); that is, you only need a USB port and a modem to connect to the Internet. Note: USB may also mean upper sideband in radio. ... SIM re-directs here; for alternate uses see Sim (disambiguation) A SIM card taken from a GSM mobile phone A subscriber identity module (SIM) is a smartcard securely storing the key identifying a mobile subscriber. ... Huawei E220 HSDPA USB modem The Huawei E220 is a Huawei HSDPA access device ( modem ) manufactured by Huawei and notable for using the USB interface (USB modem). ...


See : flat rate. Categories: Wikipedia cleanup | Stub ...


Broadband

ADSL modems, a more recent development, are not limited to the telephone's "voiceband" audio frequencies. Some ADSL modems use coded orthogonal frequency division modulation (DMT). Download high resolution version (2816x2112, 518 KB) Wikipedia does not have an article with this exact name. ... Download high resolution version (2816x2112, 518 KB) Wikipedia does not have an article with this exact name. ... Westell Model 6100 ADSL modem An asymmetric digital subscriber line transceiver, also known as an ADSL modem or DSL modem, is a device used to connect a single computer to a DSL phone line, in order to use an ADSL service. ... Asymmetric Digital Subscriber Line (ADSL) is a form of DSL, a data communications technology that enables faster data transmission over copper telephone lines than a conventional voiceband modem can provide. ... Westell Model 6100 ADSL modem An asymmetric digital subscriber line transceiver, also known as an ADSL modem or DSL modem, is a device used to connect a single computer to a DSL phone line, in order to use an ADSL service. ... Orthogonal frequency division modulation (OFDM, also called orthogonal frequency division multiplexing) is a technique for the modulation of digital information onto an analog carrier electromagnetic (e. ...


Cable modems use a range of frequencies originally intended to carry RF television channels. Multiple cable modems attached to a single cable can use the same frequency band, using a low-level media access protocol to allow them to work together within the same channel. Typically, 'up' and 'down' signals are kept separate using frequency division multiple access. An outdated model of the Motorola Surfboard cable modem A cable modem is a type of modem that provides access to a data signal sent over the cable television infrastructure. ... FDMA, or frequency-division multiple access, is the oldest and most important of the three main ways for multiple radio transmitters to share the radio spectrum. ...


New types of broadband modems are beginning to appear, such as doubleway satellite and powerline modems. Broadband in telecommunications is a term that refers to a signaling method that includes or handles a relatively wide range of frequencies, which may be divided into channels or frequency bins. ... Two-way communication between means that information is flowing in both directions between two parties. ... This article is about artificial satellites. ... For other uses, see Power band. ...


Broadband modems should still be classed as modems, since they use complex waveforms to carry digital data. They are more advanced devices than traditional dial-up modems as they are capable of modulating/demodulating hundreds of channels simultaneously.


Many broadband modems include the functions of a router (with Ethernet and WiFi ports) and other features such as DHCP, NAT and firewall features. This article is about a computer networking device. ... Ethernet is a large, diverse family of frame-based computer networking technologies that operate at many speeds for local area networks (LANs). ... Wi-Fi (or Wi-fi, WiFi, Wifi, wifi), short for Wireless Fidelity, is a set of standards for wireless local area networks (WLAN) currently based on the IEEE 802. ... DHCP in the context of computing can stand for: Dynamic Host Configuration Protocol - one of the protocols in the TCP/IP networking suite Decentralized Hospital Computer Program of the United States Department of Veterans Affairs This article consisting of a 4-letter acronym or initialism is a disambiguation page — a... In computer networking, Network Address Translation (NAT, also known as Network Masquerading, Native Address Translation or IP Masquerading) is a technique of transceiving network traffic through a router that involves re-writing the source and/or destination IP addresses and usually also the TCP/UDP port numbers of IP packets... This article is about the network security device. ...


When broadband technology was introduced, networking and routers were unfamiliar to consumers. However, many people knew what a modem was as most internet access was through dialup. Due to this familiarity, companies started selling broadband modems using the familiar term "modem" rather than vaguer ones like "adapter" or "transceiver".


Most modems must be configured properly before they can use a router. This configuration is known as bridge mode. This article or section does not cite any references or sources. ...


Deep-space telecommunications

Many modern modems have their origin in deep-space telecommunications systems of the 1960s.


Differences with deep space telecom modems vs landline modems

  • digital modulation formats that have high doppler immunity are typically used
  • waveform complexity tends to be low, typically binary phase shift keying
  • error correction varies mission to mission, but is typically much stronger than most landline modems

Voice modem

Voice modems are regular modems that are capable of recording or playing audio over the telephone line. They are used for telephony applications. See Voice modem command set for more details on voice modems. This type of modem can be used as FXO card for Private branch exchange systems (compare V.92). In telecommunication, Telephony encompasses the general use of equipment to provide voice communication over distances. ... A voice modem is a term commonly used to describe an analog telephone data modem with a built-in capability of transmitting and receiving voice recordings over the phone line. ... A Foreign Exchange Office, or FXO, is a telephone interface that receives POTS, or Plain old telephone service. ... PBX redirects here. ... V.92 is an ITU-T modem standard allowing near 56 kbit/s download and 48 kbit/s upload rates first presented in August 1999. ...


Popularity

A CEA study in 2006 found that dial-up Internet access is on a notable decline in the U.S. In 2000, dial-up Internet connections accounted for 74% of all U.S. residential Internet connections. The US demographic pattern for (dialup modem users per capita) has been more or less mirrored in Canada and Australia for the past 20 years. The Consumer Electronics Association (CEA) is the trade organization for the consumer electronics industry in the United States. ...


Dialup modem use in the US had dropped to 60% by 2003, and currently (2006) stands at 36%. Voiceband modems were once the most popular means of Internet access in the U.S., but with the advent of new ways of accessing the Internet, the traditional 56K modem is losing popularity.


See also

Image File history File links Wikibooks-logo-en. ... Wikibooks logo Wikibooks, previously called Wikimedia Free Textbook Project and Wikimedia-Textbooks, is a wiki for the creation of books. ... Wikibooks, previously called Wikimedia Free Textbook Project and Wikimedia-Textbooks, is a sister project to Wikipedia and is part of the Wikimedia foundation, begun on July 10, 2003. ... A 56 kbit/s line is a digital connection (possibly a leased line, possibly switched) capable of carrying 56 kilobits per second (kbit/s), the data rate of a normal single channel digital telephone line in North America. ... BBN Technologies (originally Bolt Beranek and Newman) is a high-technology company that provides research and development services. ... Broadband in telecommunications is a term that refers to a signaling method that includes or handles a relatively wide range of frequencies, which may be divided into channels or frequency bins. ... It has been suggested that this article or section be merged with satellite dish. ... Asymmetric Digital Subscriber Line (ADSL) is a form of DSL, a data communications technology that enables faster data transmission over copper telephone lines than a conventional modem can provide. ... A cable modem is a special type of modem that is designed to modulate a data signal over cable television infrastructure. ... For other uses, see Power band. ... Command and Data modes refer to the two modes in which a computer modem may operate. ... In telecommunication, the term dial-up has the following meanings: Dial-up access, typically to the Internet A service feature in which a user initiates service on a previously arranged trunk or transfers, without human intervention, from an active trunk to a standby trunk. ... Look up driver in Wiktionary, the free dictionary. ... DHCP in the context of computing can stand for: Dynamic Host Configuration Protocol - one of the protocols in the TCP/IP networking suite Decentralized Hospital Computer Program of the United States Department of Veterans Affairs This article consisting of a 4-letter acronym or initialism is a disambiguation page — a... Ethernet is a large, diverse family of frame-based computer networking technologies that operate at many speeds for local area networks (LANs). ... This article or section does not cite its references or sources. ... An INF file (or Setup Information file) is a plain text file used by Microsoft Windows for installation of software/hardware. ... The Internet protocol suite is the set of communications protocols that implement the protocol stack on which the Internet and most commercial networks run. ... This article or section is in need of attention from an expert on the subject. ... V.92 is an ITU-T modem standard allowing near 56 kbit/s download and 48 kbit/s upload rates first presented in August 1999. ... K56flex (originally called the K56Plus) was a modem chipset from Rockwell and Lucent that gave users the possibility of receiving data on ordinary phone lines at 56 kbit/s as opposed to the previous maximum of 33. ... For other uses, see Modulation (disambiguation). ... Plug and Play is a term used in the computer field to describe a computers ability to have new devices, normally peripherals, added to it without having to restart the computer. ... RJ-11 (Registered Jack 11) is a physical interface often used for terminating twisted pair type cables. ... US Roboticss 56K modem protocol for upload under V.34+ at 33. ... Zeroconf or Zero Configuration Networking is a set of techniques that automatically create a usable IP network without configuration or special servers. ...

References

  1. ^ IEEE History Center. Gottfried Ungerboeck Oral History. Retrieved on 2008-02-10.
  2. ^ Modem compression: V.44 against V.42bis
  3. ^ http://fndcg0.fnal.gov/Net/modm8-94.txt
  4. ^ Data communication over the telephone network
  5. ^ About bonding modems

2008 (MMVIII) is the current year, a leap year that started on Tuesday of the Common Era (or Anno Domini), in accordance with the Gregorian calendar. ... is the 41st day of the year in the Gregorian calendar. ...

External links

Wikimedia Commons has media related to:
Modems

Standards Organizations and modem protocols

FCC redirects here. ...

General modem info (drivers, chipsets, etc.)

Other

Telephone network modem standards

ITU V-Series | V.92 | K56flex | X2 | MNP | Hayes command set Image File history File links Motorola_modem_28k. ... This article or section is in need of attention from an expert on the subject. ... V.92 is an ITU-T modem standard allowing near 56 kbit/s download and 48 kbit/s upload rates first presented in August 1999. ... K56flex (originally called the K56Plus) was a modem chipset from Rockwell and Lucent that gave users the possibility of receiving data on ordinary phone lines at 56 kbit/s as opposed to the previous maximum of 33. ... X2 was a 56 kbit/s modem protocol developed by US Robotics, and competed in a format war with Lucent and Rockwells joint K56flex protocol until the adoption of the V.90 standard. ... The MNP (Microcom Networking Protocol) family of error-correcting protocols were commonly used on early high-speed (2400 bps and higher) modems. ... This article or section does not cite its references or sources. ...

ISDN redirects here. ... DSL redirects here. ... // The term cable Internet access or Cable Internet refers to the delivery of Internet service over this infrastructure. ... Fiber to the x (FTTX) is a generic term for any network architecture that uses optical fiber to replace all or part of the usual copper loop used for telecommunications. ... For other uses, see Power band. ... Wi-Fi (IPA: ) is the common name for a popular wireless technology used in home networks, mobile phones, video games and more. ... This article is about the electronic protocol. ... See http://en. ... WiBro (Wireless Broadband, Korean: 와이브로) is a wireless broadband Internet technology being developed by the Korean telecoms industry. ... Official WiMax logo WiMAX, the Worldwide Interoperability for Microwave Access, is a telecommunications technology aimed at providing wireless data over long distances in a variety of ways, from point-to-point links to full mobile cellular type access. ... UMTS-TDD is a mobile data network standard built upon the UMTS 3G cellular mobile phone standard, using a TD-CDMA, TD-SCDMA, or other 3GPP-approved, air interface that uses Time Division Duplexing to duplex spectrum between the up-link and down-link. ... High-Speed Packet Access (HSPA) is a collection of mobile telephony protocols that extend and improve the performance of existing UMTS protocols. ... Evolution-Data Optimized or Evolution-Data only, abbreviated as EV-DO or EVDO and often EV, is one telecommunications standard for the wireless transmission of data through radio signals, typically for broadband Internet access. ... Satellite Internet services are used in locations where terrestrial Internet access is not available and in locations which move frequently. ... For other uses, see Infrared (disambiguation). ...

  Results from FactBites:
 
What is modem? - A Word Definition From the Webopedia Computer Dictionary (1295 words)
A modem is a device or program that enables a computer to transmit data over, for example, telephone or cable lines.
While the modem interfaces are standardized, a number of different protocols for formatting data to be transmitted over telephone lines exist.
Modems that support a voice/data switch have a built-in loudspeaker and microphone for voice communication.
Modem - Wikipedia, the free encyclopedia (5557 words)
A modem (a portmanteau word constructed from modulator and demodulator) is a device that modulates an analog carrier signal to encode digital information, and also demodulates such a carrier signal to decode the transmitted information.
Modems are generally classified by the amount of data they can send in a given time, normally measured in bits per second, or "bps".
Modems in the United States were first introduced as a part of the SAGE air-defense system in the 1950s, connecting terminals located at various airbases, radar sites and command-and-control centers to the SAGE director centers scattered around the US and Canada.
  More results at FactBites »

 
 

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