Wireless companies say they’ve been told their signals may be jammed during the G8 and G20 summits, but aren’t being given any more information about how thousands of cellphone users could be affected.

While the G8 summit is in Ontario cottage country, the G20 is in the heart of downtown Toronto, and widespread shutdown of cellphone networks could wreak havoc on businesses already preparing to take a hit from security precautions in place for the meetings.

But the technology is expected to be used only to create a moving bubble of electronic silence around motorcades.

“No one will be informed of locations and times for security reasons,” said one wireless industry source.

The Integrated Security Unit responsible for the summits wouldn’t comment on security plans.

“We use a lot of different techniques in ensuring security to deal with possible threats and we never share those techniques, we don’t make them public,” said Sgt. Leo Monbourquette, a spokesman for the ISU.

In order to jam the signals, the RCMP must apply for an exemption from the Radiocommunications Act, which generally forbids interfering with the airwaves.

It’s unknown whether they’ve applied for one for the summits, as approvals are only published after the fact. But the first RCMP exemption was for the 2002 G8 Summit in Kananaskis, Alta.

Often, the wireless industry itself receives no advance notice at all, said Marc Choma, director of communications for the Canadian Wireless Telecommunications Association.

But what interference there may be rarely lasts long, he said.

“The thing with jamming technologies, because a lot of law enforcement themselves, their communications, are wireless as well, you’d have to try and specify what kind of frequencies that you were trying to jam,” he said.

“The jamming is not precise, you can’t say I only want it to go one metre and three centimetres, so it could be going farther than you think. There is possibility it would interfere with other types of communications.”

With cellphones and remote controls often tools of choice for setting off bombs, jammers have become a regular security tool at major national and international events.

A search of orders-in-council shows the RCMP most recently received an exemption from the act for the visit of Israeli Prime Minister Benjamin Netanyahu at the end of May.

They were also granted an OK for the 2010 Winter Olympics in Vancouver and Whistler, B.C.

A spokesperson for the RCMP-led Integrated Security Unit which oversaw the Games wouldn’t say whether the technology was actually used for the Olympics.

An exemption is often applied for just in case the power is needed, said Dawn Roberts.

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But even if it had been deployed, cellphone users may never have noticed, she said.

“It may appear as a dropped call,” she said.

“A lot of the cellphone action is very site-to-site directional. Walking past a high rise building could have the same the effect. It’s not as if a big bubble goes out and we have a cone or dome that’s widespread.”