Roanoke Times
Copyright (c) 1995, Landmark Communications, Inc.
DATE: THURSDAY, June 29, 1995 TAG: 9506290023
SECTION: EXTRA PAGE: 1 EDITION: METRO
SOURCE: JOEL ACHENBACH
DATELINE: LENGTH: Long
A: These days you are always told, before takeoff, to fasten (not buckle, fasten) your seat belt, close your tray table, raise your seat to its full and upright position, and turn off any electronic devices that might send a stray signal into the cockpit and cause the plane to fly upside down.
Actually that last part isn't explicitly spelled out. The flight crew leaves it to your imagination. (So you look over at the 7-year-old kid frantically destroying alien spaceships on his Nintendo game, and your imagination says: Perhaps the train would have been wiser.)
With several recent plane crashes remaining unexplained, attention has turned to electronic gadgets as possible culprits. Laptops, Gameboys, portable CD players and cellular phones have proliferated madly in just the last few years, and pilots increasingly worry that the gadgets can produce electromagnetic interference in the plane's navigational system.
Cellphones, remote-control devices and anything else that intentionally transmits a signal are banned throughout the flight. (Sorry, fellas, you have to leave the beloved TV remote at home.) The other portable devices, which emit radiation in a more random and unintentional fashion, are supposed to be turned off when the plane is under 10,000 feet.
But do these things pose a real danger? Or is this just a silly scare that'll fade with time? It's hard to know. For the moment there's no proof that these things are dangerous.
If nothing else, airlines think the physical presence of the devices is dangerous during takeoff and landing, because they can go flying through the air and whack someone on the noggin. So the airlines tell you to put them away.
As for the scarier scenario, it's hard to know what's real and what's coincidental. There are numerous anecdotes from pilots of oddities in the cockpit that might be linked to portable electronic devices on board. On the other hand, these effects have never been duplicated in a laboratory setting.
An example of what might go wrong: In November 1994 a British Airways jumbo jet mysteriously started banking off course. The pilot regained control only after a passenger using a compact camcorder switched it off.
Time magazine in 1993 reported that a plane leaving Chicago veered off course and its cockpit dials went haywire until a passenger turned off his laptop computer.
And the London Times earlier this year reported that electromagnetic interference with the plane's on-board computers might have caused a 1991 crash in Thailand that killed 223 people. The article, however, did not provide any documentation of that suspicion.
We contacted an organization called RTCA, formerly the Radio Technical Commission for Aeronautics. Within RTCA, the ``Special Committee 177'' is doing a study on electromagnetic interference for the Federal Aviation Administration. (As you know, this updates an earlier study by Special Committee 156.)
The investigators have concluded for the moment that it's highly unlikely that an electronic gadget can affect a plane's navigational system. Not impossible, mind you, but definitely a long shot.
This is the deal: Planes have antennas that pick up navigational data from ground-based transmitters. The concern is that radiation from an electronic device in the passenger cabin will go out the window and bounce off something like a wing or a tail and ricochet into one of the plane's antennas.
But keep in mind that just because something is giving off a signal doesn't mean the plane's antennas are tuned to that bandwidth.
How likely is it that everything could go wrong and a pulse from your Gameboy could cause a needle to wiggle in the cockpit? The Special Committee calculated the odds at .00000067.
It's probably more likely you will be crushed by the beverage cart.
Q. Why do computer modems make that awful hissing noise?
A. Don't worry, we aren't going to turn into the CyberTechDork column. We promise that next week we will take a step back and explain something simpler, like why the Romans chiseled a ``U'' as though it were a ``V.''
A computer modem (for ``modulator-demodulator'') hisses for two reasons. First, it's using a telephone technology that requires the modem to be audible. The computer is piggybacking on Alexander Graham Bell's gadget. It takes a stream of data and converts it into audible tones.
As for why it doesn't make a nicer sound: Because it's sending lots of information fast. A few years ago, with the slowest modems, you could actually hear the individual tones, like someone pressing buttons on the phone very rapidly. Now modems are many times faster and all you hear is the hiss of data streaming into the phone line.
That said, modems are silent after they finish the ``handshake'' with the computer on the other end of the line. The annoying hiss only lasts a few seconds while the two computers figure one another out. Then the modem goes silent.
You can, in fact, program your modem to be silent throughout the process. But manufacturers have designed modems to be audible so that you can tell that you've reached another computer and that the two computers are speaking the same (hissing) language.
- Washington Post Writers Group
by CNB