Modems

Modem Overview

Modem is an acronym for Modulator Demodulator. A modem is a device that converts data from digital computer signals to analog signals that can be sent over a phone line. This is called modulation. The analog signals are then converted back into digital data by the receiving modem. This is called demodulation. A modem is fed digital information, in the form of ones and zeros, from the CPU. The modem then analyzes this information and converts it to analog signals, which can be sent over a phone line. Another modem then receives these signals, converts them back into digital data, and sends the data to the receiving CPU.

Understanding V.90 Technology

Traditional modem standards assume that both ends of a modem session have an analog connection to the public switched telephone network.

Data signals are converted from digital to analog and back again, limiting transmission speeds to 33.6Kbps (Thousand Bits Per Second) with current V.34 modems, and due to limitations of the public telephone network the theoretical maximum is 35Kbps Now with V.90 technology a different assumption is made: that one end of the modem session has a pure-digital connection to the phone network (which Internet Service Providers and corporations already use for remote access) and takes advantage of that high-speed digital connection.

By viewing the public switched telephone network as a digital network, V.90 technology is able to accelerate data downstream from the Internet to your computer at speeds of up to 56Kbps. In this way V.90 technology is different than other standards of today, because it digitally encodes downstream data instead of modulating it as analog modems do.

The data transfer is an asymmetrical method, so upstream transmissions (mostly keystroke and mouse commands from your computer to the central site, which require less bandwidth) continue to flow at the conventional rates of up to 33.6Kbps. That is upstream data (Data sent from your modem) is sent as an analog transmission that mirrors the V.34 Standard. Only the down stream data transfer takes advantage of the high speed V.90 rates V.90 technology is ideal for Internet users, because you really need the 56Kbps speed for downloading of Web pages with sound, video and other large files.

All that is needed is for your V.90 modem to be connected to an ISP or corporate site using V.90 technology over their digital lines to the network. Note: Modems can receive data at speeds of up to 56Kbps however due to FCC (Federal Communications Commission) rulings on maximum permissible transmit power levels during down load transmissions; speeds of 54Kbps are the maximum. Actual data speeds received will vary depending on line conditions.