Black Box manual 4 of, V.90 technology, x2 technology, V.92 technology, Technically Speaking

Technically Speaking

In the last 20-some years, phone companies have been replacing portions of their original analog networks with faster digital circuits, which encode information as either a binary one (1) or zero (0). But the slowest portion of the PSTN to be overhauled is the one you’re most familiar with: the connection from your home to the phone company’s central office . As a result, bottlenecks occur when you’re trying to to surf the Internet or perform remote access from home. Why the slowdown?

Conversion. Data-transmission speeds are reduced when analog signals on one end of the link are converted to digital and then back to analog on the other end of the link. The difference between the original analog waveform and the reconverted signal is called quantization noise. It limits the analog data-communication channel to about 35 kbps.

V.34+ modems, with top speeds of 33.6 kbps, avoid the analog-to-digital hassles. They treat the PSTN as if it were entirely analog, avoiding all the conversion slowdowns.

However, since one end of the connection is completely digital (the phone company’s), V.34+ modems aren’t making the most of the available bandwidth—and the digital bandwidth to be exploited is nearly 64 kbps.

V.90 technology

V.90 gets around the problem. Quantization noise affects only analog-to-digital conversions, not digital-to-analog. There are no analog-to-digital conversions between a V.90 digital modem and the PSTN, and the digitally connected transmitter uses only the 256 discrete 8-bit PCM (pulse code modulation) codes available on the digital portion of the phone network. So the digital information from the PSTN reaches the V.90 analog modem’s receiver intact, so you can download at speeds up to 56 kbps. (In the U.S., the FCC limits the actual speed to 53 kbps.) Note that a V.90 analog modem’s upstream, or send, channel does not go through an analog-to- digital conversion, limiting it to V.34+ speeds.

x2 technology

U.S. Robotics V.90 modems are compatible with its proprietary 56K technology, x2. With x2, you can download information nearly twice as fast as with ordinary V.34 modems and reduce waiting time. When your service provider

upgrades to the V.90 standard, you can upgrade your modem with a simple flash download.

And when using an x2 faxmodem for telecommuting, you can speed up the delivery of information, which means you can access databases, get your e-mail, and access corporate Intranets faster, without investing in new equipment.

V.92 technology

With the introduction of x2 technology in 1997, U.S. Robotics introduced a marked change in the ease and availability of Internet data. The subsequent V.90 standard unified the data communications industry in its approach to providing dialup access to remote data.

Next came the V.92 standard. It improves the achievements of both x2 and V.90 technologies by making access to the Internet even simpler and less expensive.

The V.92 standard enhances V.90 in three major ways:

•It provides a faster, more balanced upstream to complement the 56 kbps downstream rate found in x2 and V.90 technologies.

•It defines a mechanism for significantly shortening the dialup connection time.

•It provides a method for effectively sharing a data line

with voice functionality.

A V.92 modem “remembers” the connection conditions each time and tests for similar conditions each time it connects. If the conditions match those from the last time the modem was used, V.92 restores the previous connection, cutting 30 to 50 percent off the normal training time. In the case of a typical desktop computer setup, which often dials the same ISP point of presence from the same phone line every time, this situation will be common.

Whether you’re ready for the power of V.92 depends a lot on your ISP. Does it currently support the new V.92 technology? Even if it doesn‘t, you can take advantage of Internet Call Notification (ICN) now. ICN enables you to identify callers attempting to reach you while you’re on-line. And because V.92 is backward compatible to older technologies, you’ll be ready to enjoy the benefits of V.92 as soon as your ISP upgrades.

5/1/2007	724-746-5500	blackbox.com
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