Chinese electronics firm C.T.S. Technology Co. is facing a possible record $34.9 million fine from the Federal Communications Commission for illegally selling 285 kinds of signal-jamming devices to U.S. customers for more than two years.

The New York Times reports the fine was calculated by multiplying the maximum fine, $122,500, by the number of devices sold. The company, based in Shenzen, has a retail Web site that alleged some signal jamming devices were legal.

Signal jammers interfere with authorized communications, including Wi-Fi networks, cell phones and GPS systems.

The FCC said undercover agents bought 10 devices from C.T.S.

“All companies, whether domestic or foreign, are banned from marketing illegal jammers in the U.S.," Acting Chief of the Enforcement Bureau Travis LeBlanc said in a statement. "Signal jammers present a direct danger to public safety, potentially blocking the communications of first responders. Operating a jammer is also illegal, and consumers who do so face significant civil and criminal penalties.”

The FCC says not only is use of such devices illegal, it's also illegal to "advertise, sell, distribute or otherwise market these devices to consumers in the United States."