In certain towns (generally near military bases), on certain days (such as the day an aircraft carrier returns to port), keyless car entry systems and remote garage door openers mysteriously fail. While some frustrated motorists blame aliens, the FCC says the jammed frequencies belong to the U.S. military.

Keyless entry remotes have become standard in new cars in recent years. Of the more than 14 million cars and light trucks produced in the United States last year, 77 percent came with the remotes, up from 32 percent in 1996, according to industry research company

The technology is similar to that used in garage door openers and remote-controlled toys. The remote acts as the transmitter, sending an encrypted message on a weak radio signal to the receiver in the car, which decodes the message and activates door locks and other functions.

But unlike other more powerful radio signals, keyless entry remotes are not licensed by the Federal Communications Commission. They are allowed to operate on frequencies used by licensed customers as long as their signals are sufficiently weak and don’t interfere with others. But because of this outlaw status, their own signals can be jeopardized.

“Car entry systems, they have no rights at all,” said Bruce Romano, who works in the office of engineering and technology at the FCC. “If they get interference, that’s too bad for them.”

Interference can occur when a stronger signal on the same or similar frequency overwhelms the receiver, and the low-powered message from the remote cannot be “heard.” An engineer compared the situation to trying to have a conversation at a stock car race, where the roar of the vehicles will drown out the voices.

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