Does it make any difference whether you buy a cheap modem or an expensive modem? Yes. And no.
If you are really high-tech in the way you're sending or receiving data, it may not make any difference at all.But if you buy a cheap modem and use it for run-of-the-mill, not-so-high-tech telecommunication, you may end up paying more in phone and on-line charges than you save on the modem's cost.
We put three new modems to tough tests. We selected models with performance-enhancing circuits not found in the makers' basic models. We tested them with and without their extra features. And the results surprised us.
One modem is the high-end U.S. Robotics Courier v.32bis 9600-baud modem. We use it for our online research and for transmitting these columns to the newspapers that run them. It retails for $895.
We compared it with Microcom's best portable 9600-baud modem, the MicroPorte 4232bis, which lists for $649, and with Computer Peripherals' high-end $549 9600-baud VIVA 9642e. All three modems employ V.32bis, V.42bis, LAPM and MNP 5.
Modem terminology is as jargony is English can get, but the concepts they hide are simple. The term V.32bis is one of a set of technical standards that keep modems from fighting at opposite ends of a phone line. Saying V.32 is about like saying that a modem's speed is 9,600 baud.
Baud, an old speed measure, is being replaced by bps (bits per second). In computer code, each English letter translates into eight computer bits. In modem shopping, you may encounter bauds and bps.
At 9600 bps, we can send a subscriber a column in four seconds . . . theoretically. With modems, nothing ever performs at theoretical levels. We've never squeezed one of these babies over a phone line in less than 12 seconds - plus the time modems take to signal and recognize each other.
Telephone lines are imperfect. They can distort digital signals. So modems, or the software that helps them work, are made so they can watch for and correct errors. One of the newest ways modems do that is defined by a standard called MNP 5.
MNP 5 is a newer, better version of MNP 4, MNP 3, MNP 2 and MNP 1. (There's also MNPs 6, 7, 9 and 10. Somebody skipped 8. Don't ask us why.) It's defined in a standard called V.42, which covers modems' error-correcting methods.
Besides MNP, there's a competing error correcting method known as LAPM. Some modems offer LAPM and some offer MNP. The most full-featured modems include both, since few modems that don't use the same method can work together to correct errors - even if both claim to be V.42 compliant.
So don't spend extra money to get a V.42 modem unless it handles both LAPM and MNP 5. Monitoring and fixing errors takes time. In modems using MNP 1 and MNP 2, data transmission time is slower by as much as 30 percent. To make up for that, modem makers started looking for ways to make the same data take up less room as it moves across telephone wires.
The solution: Get rid of unneeded bits of data. In jargon, they call it data compression. A modem does data compression if its maker puts bis after the V.32 or V.42. So a V.42bis modem is one that uses LAPM or MNP 3, 4 or 5 error correcting and compresses data while sending it.
Your modem can only use V.42 if your telecommunications software can get out of the way and let it handle error-correcting. Most good older telecom software can't do that. So unless yours is fairly new, you may not be able to use the V.42 power even if you pay for it.
Beware when buying! V.42 and V.42bis do not refer to any specific modem speed. A slick modem peddler can say its modem is V.42 or V.42bis compliant when it's as slow as 1200 bps. That's at least eight times slower than a 9600 bps modem.
If you want a 9600 bps modem that compresses data before sending and decompresses it after receipt, buy a V.32bis. Because the compression boosts effective speed, you get a bonus: These modems can really send and receive data at speedy 14,400 bps.
The two most common types of data transfer (protocols) for using V.42 in telecom software are called Y Modem and Z Modem. We tested them - and others - in our Relay for Windows telecom program. Best, from our tests, turned out to be a modified protocol called Y ModemG.
Our tests used phone hookups that let us selectively use the features in V.32bis and V.42bis. Our biggest surprise was that when we used full V.32bis and V.42bis power, all three modems sent and received the test file in exactly the same time: 1 minute 26 seconds.
The file is a computer program 50 times as big on disk as one of these columns. It has a built-in self-test that shows if it's accurately transmitted. So next, we sent and received the same file after we deactivated the error-correction and compression power of the V.42bis.
With each modem connected to Relay and the same computer, that same test file took anywhere from 8 minutes 3 seconds up to 9 minutes 13 seconds to send. The more expensive the modem, the faster the transfer was.
So here's our conclusion. If you know you'll only be communicating with other modems that have V.32bis and full V.42bis power, go ahead and buy cheap. But if, like us, you telecommunicate with a raggedy assortment of friends and other folks, you'd better believe that you get what you pay for.
Some of the information services we connect with charge several bucks a minute. At that, we can earn back the difference between $895 and $549 in a few months.