FAQ's
Frequently Asked Questions

What is V.90 Technology?

It's a 56K modem standard . . .

In 1998, 56K modems finally reached critical mass, after the V.90 modem standard was declared by the ITU (the international standards organization) in February. Modem makers quickly began shipping V.90 compliant products. The V90 roll-outs are now complete by most major ISPs, and consumers have adopted widespread use of V.90 modems.

The petty X2 versus K56flex battle of 1997 is now completely irrelevant and has subsided, but the V.90 saga is just beginning. Stay tuned to V90.com for all the latest news and information about the fast (and the last) analog modem standard.

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. (Read How V34 and V32 Modems Work for a historical perspective) 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 a 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.

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.

Why can't I connect at 56kbps?

For all the buzz about how 56k will change your life, a lot can go wrong. Even the technology's name is little more than wishful thinking: you won't achieve 56 kbps, even under the best conditions, for technological and bureaucratic reasons. To help you understand why, we've assembled a list of all the potential barriers between you and that magic number. To understand some of these roadblocks, however, you need a handle on how 56k technology actually works.

Roadblocks on the way to 56k

Both 56k specifications used today take advantage of nuances in the way the phone system is designed. In a standard call between two modems, your data must be translated into analog "tones" before it can be transmitted across the telephone network. This translation is called the digital-to-analog conversion. Once your data reaches a telephone company's central office, it's translated back to digital form by a coder/decoder (codec) for transmission across the phone company's digital backbone. Unfortunately, because the telephone network contains some random noise, the analog-to-digital conversion is only an approximation of the original digital signal. To ensure that data remains readable despite the effects of this quantization noise, transmission rates are currently limited to about 53 kbps.

However, because most Internet service providers (ISPs) connect directly to the phone company's digital backbone using routers, data coming from an ISP never need undergo an analog-to-digital conversion. Instead, the data can be encoded (using pulse code modulation or PCM) so that it remains entirely digital until it gets to the central office. Once it arrives, the data is put through a digital-to-analog conversion before being sent across the analog phone lines to your modem. And, because digital-to-analog conversions aren't affected by quantization noise, the result--in theory, at least--is throughput as high as 56 kbps from the ISP to you.

The bad news? Anything that adds noise to the telephone line or causes an analog-to-digital conversion between your ISP and your modem lessens the transmission's performance. Worse than that, if there's nasty noise on the phone line, your only solution may be to move. Scream all you want, but the telephone company is obligated only to provide you with a clean enough line to get 4,800-bps data rates. But those aren't your only potential troubles.

The FCC says "no more than 53 kbps"

Though your modem says it's "56k," you won't get throughput that fast, thanks to a speed limit set by the FCC (Federal Communications Commission). The reason for that regulation? Sending a signal down a telephone wire requires electrical power. But the more power you apply, the greater the chance of a problem called crosstalk. You've encountered this annoyance if you've ever heard other people's conversation during a phone call. To help prevent crosstalk, the FCC limits the amount of power that phone companies can use to send signals over the network. And this cap on signal strength limits data throughput to a maximum of 53 kbps, regardless of what your modem can actually deliver. The FCC is currently reviewing this ruling and may overturn it later this year to enable true 56-kbps modem connections.

Office PBX systems

If you have to dial 9 to get an outside line, your office uses a digital PBX telephone system, which means you also won't be able to achieve 56k rates. A PBX system incorporates a codec that performs an analog-to-digital conversion so that your calls can be stored digitally on magnetic media, such as hard disks. Though this system gives you some great features, such as employee extensions and call forwarding, it also limits your 56k calls to a maximum throughput of about 35 kbps.

Noisy analog lines

Digital lines usually don't suffer from noise problems, but the analog wires between the phone company's central office and your home are a different story. If you hear buzzing or static when you listen through your phone's headset, chances are you won't be able to achieve optimum modem speed. Caller ID, answering machines, and cordless phones can add even more noise to your line. To minimize the hum try disconnecting these types of devices one by one and listening again to determine which, if any, are the source of the problem. If this doesn't work, your line noise may be caused by nearby power lines or other environmental or structural factors. In that case, call the phone company and complain (good luck). In our testing, we injected white noise called intermodulation distortion, which is similar to what you might encounter over analog lines.

Central office switch-ups

Connections between local central-office switches can sometimes be a problem. Old equipment may require analog termination, resulting in an analog-to-digital conversion as the call goes through to the next switch. If a local call to your Internet service provider gets routed through these "partially analog" switches, you'll lose 56k capability. If that happens, the telephone company may be able to tell you which type of switches your call gets routed through on the way to your ISP. (One such problem switch is the AT&T 1AESS. However, the AT&T 5ESS and the Northern Telecom DMS-100/500 switches should both work fine.)

When you make a long-distance call, you can be sure it's traveling only through digital switches. The long-distance network in the United States is, thankfully, a fully digital system. Transcontinental calls, however, use digital ADPCM encoding for voice compression, which doesn't work with 56k PCM encoding. So you won't be able to get the higher throughput rates when calling another continent.

Trouble in the office-to-home commute

A number of problems can occur as data makes its way from the local central office to your home. Older telephone lines connect directly to the switch at the central office, and newer lines go through a digital loop carrier (DLC). These devices can combine 96 separate lines into one before they reach the central-office switch. By using DLC, the telephone company doesn't have to bury as much expensive copper wire, which saves money and increases connection reliability. But DLCs can wreak havoc with 56k. If the DLC is digitally connected to the switch, no problem; but if it uses a universal connection, an analog-to-digital conversion will occur, rendering your modem's 56-kbps capabilities useless.

There may also be a "pad" between you and the central office. A pad balances the volume on both ends of the line when you make a call. If the pad occurs before the signal is converted to analog, you'll see only a slight degradation in 56k performance. But if you encounter an analog pad between the central office and your home, up crops another analog-to-digital conversion to sabotage your 56k connection. In our tests, we introduced digital pad impairments to see how each 56-kbps modem handled them; for the most part, the products did not find them too bothersome.

Some local lines also run through an amplifier called a load coil to boost the signal rates across longer distances. Load coils cause some signal distortion and will detrimentally affect your modem's 56k throughput potential. During testing we also tested a long local loop containing a load coil. Though many of the products fell back to 28-kbps rates, others handled this impairment without great performance loss.

Connect for success

Your Internet service provider must have a fully digital connection to the telephone company's central office for 56k technology to work. This means that the ISP must have either ISDN or a T1 or T3 line. ISDN is guaranteed to be digitally terminated, but T1 lines can be broken out into 24 separate analog lines. This setup requires an analog-to-digital conversion at the ISP's end and will prevent you from getting 56k speeds.

In the case of 56k technology, ISDN has another advantage over T1. ISDN generally uses out-of-band signaling, in which a separate channel is used to synchronize the flow of data and set up the call, thereby freeing the line's entire bandwidth for sending data. T1 lines use what is known as robbed-bit signaling. In that method, a bit of the incoming data is stripped off to indicate the status of an incoming or outgoing call and to synchronize the data flow, slightly reducing your maximum throughput.

Why does Windows always report my connect speed as 115,000 instead of the true connect speed, which is probably 46,000 or 48,000?

Windows is reporting the DTE to DCE speed-- the speed at which Windows is talking to your modem, not the speed at which your modem is talking to the modem at the other end of the line. The Windows serial port is talking to the modem at 150,000 bits per second, and your modem is only talking to the outside world at 56K (which is itself a very optimistic number, as 56K is the maximum connect speed, not the regular connect speed).

Which init string is correct? You'll have to find that out on your own, since every modem is different. Go to AccessOne's site, which lists init strings for all modems.

Linus Torvalds, a very cool guy and sometime Screen Saver guest, wrote the Linux operating system while he was a college student at the University of Helsinki in Finland. Instead of making it proprietary and trying to sell it, Torvalds gave it away, so anyone who wanted to develop for it could do so. As a result, thousands of people all over the world have worked on Linux, and it has become a very sophisticated, complex, and powerful operating system. It is available as a free download or, for a nominal fee, on CD-ROM.

But don't run out and download Linux just because it's free. It's not a consumer operating system, and it requires a very high level of skill to install and run. It's a flavor of the Unix operating system-- on which most of the Internet runs-- and is mainly used by programmers as a development tool.

Think of an operating system like the levels of the Titanic. At the bottom there are the steamroom workers who keep the ship moving; they're the BIOS. The next level up, you have the employees and attendants; the hardware. Above that, you have all the decks with passengers; the applications. Like Windows, Linux has applications, but it's as different from Windows as a Mac is from a PC. Windows documents cannot necessarily be read by Linux, and Windows programs cannot run on Linux. Most distributions of Linux don't have a graphical user interface, meaning no friendly buttons, and no pick-and-choose menus.

Knowing Unix is a very valuable skill, so if you want to learn, using Linux is the way to go. You'll need to get one of the many different versions of Linux, which are called distributions. Leo recommends the Red Hat Distribution, from Red Hat Software. It seems to be Linus Torvalds' favorite as well. The Red Hat Distribution is one of the easiest to install, and has the most complete set of tools.

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