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A modem (a portmanteau constructed from modulate and demodulate) 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. Experiments have even been performed in the use of modems over the medium of two cans connected by a string.

The most familiar example of a modem turns the digital '1s and 0s' of a personal computer into sounds that can be transmitted over the telephone lines of Plain Old Telephone System (POTS), and once received on the other side, converts those sounds back into 1s and 0s. Modems are generally classified by the amount of data they can send in a given time, normally measured in bits per second, or "bps".

Far more exotic 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 optic fibers. Most intercontinental data links now use optic modems transmitting over undersea optical fibers. Optical modems routinely have data rates in excess of a billion (1x109) bits per second.

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56k=v.Unreliable - News and information about 56k modems. Extensive troubleshooting section.
Meta Description: [ Modemsite.com (formerly 56k=v.Unreliable): Internet Connectivity, Modem Drivers, Troubleshooting Connection Problems. This is the Top page of the site. ]

AirLink Communications, Inc. - Manufacture CDPD modems, test tools, and vehicle tracking and telemetry systems. Includes product specifications and applications, and career opportunities.

Allied Data Technologies - Dutch Modem and ISDN peripherals. Brandnames TRON Tornado Bausch Trident
Meta Description: [ Allied Data Technologies is a Dutch manufacturer of datacom and other communication applications, including ADSL Modems, Routers, VoDSL IAD's, ISDN equipment, PC Modem Cards, Remote Access Servers etc. Custom-made or Retail products of OEM or Embedded modems, ISDN solutions and xDSL CPE. ]

ARC Electronics - SCADA applications including dial up, leased line modem, cellular modems and wireless

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Meta Description: [ Review: using a cellular modem with a Dell Latitude CPt C333GT notebook/laptop portable computer - a hands-on experience exploring the use of notebook computers with cellphones. ]

IP-Warehouse - Simple Source for IP Networks. Dslam DSL equipment online sales.
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Meta Description: [ A comprehensive source of information on modems, emphasizing practical advice on how to select and use them effectively. ]

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