Expert readers weigh in on anti-cellphone tactics

By BILL HUSTED

Cox News Service

December 19, 2004

I'm never sure which questions will spark an avalanche of reader response.

It's great fun when that happens. Recently I answered a question from a restaurant owner interested in a jamming device to prevent cellphones from operating inside his restaurant.

I told him jamming cellphones in the United States is illegal and offered the opinion that metal shielding — which can block the transmissions — might be legally OK. I worried, however, there might be legal problems with advertising that the restaurant was blocking the signals on purpose. I have done more research — my answer seems to hold up — but I will be able to elaborate a bit at the bottom of this column.

First, we'll let the readers speak. I've boiled down the e-mails so I can get in as many as possible. Even so, there's not room for all of them, and I apologize.

Bob Harbort, a Ph.D. and professor of engineering at Southern Polytechnic State University in Marietta, Ga., suggests a Faraday cage — basically, a shield that will stop radio waves. He said any possible legal problems about advertising the shield could be handled with a warning to customers that, because of construction, cellphones won't work inside.

Greg Vaught of San Antonio, manager of a restaurant, said: "I have had it with cellphones. I was disappointed that you didn't make what is to me the most obvious point: The guy says he manages the restaurant. If so, he can institute a no-cellphone policy, prominently display the message, and politely but firmly enforce it."

Bill Waugaman of Palm Coast, Fla., worries that any jamming of cellular phones could have unintended consequences. He noted that jamming cellphone frequencies would "also interfere with any 800-MHz public safety radios, used in many major cities. This presents a whole range of liabilities to the business owner should he or his patrons require any assistance from police, fire or medical services, not to mention a lack of civic responsibility.

"Using RF-excluding building materials would have the same effect at all frequency bands, preventing all [radio frequency] devices, including pagers and BlackBerries, from properly operating in his establishment. Would an on-call physician or any other on-call professional patronize his establishment knowing their pager or alerting device would not work?"

Greg Darnell wrote to say that "international law and FCC regulations match your comments with respect to jamming [which is the transmission of spurious electromagnetic energy intended to disrupt communication]. However, your other advice, I believe, is off-target. What you speak of as 'passive jamming' [lead lining, etc.] isn't jamming. It's called shielding. Shielding is not illegal. Casinos apparently incorporate shielding in their construction to eliminate radio communications to or from points within their buildings."

Those are some of the things readers had to say.

Here's what I've discovered from my own research: Active jamming is definitely illegal.

There's no law that regulates shielding against radio signals. However, here's the real kicker: It wouldn't be feasible to create a Faraday cage that would shield a restaurant that has windows. At the very least, metal screens would have to cover all windows to block cell signals.

It seems to me that Vaught's response is the best one.

Many public places post signs requiring that cellphones be turned off. I doubt that will stop all calls, but — if actively enforced — it should quiet things down.