The US Federal Communications Commission has issued warnings to 20 online retailers selling illegal mobile phone jammers, GPS jammers, Wi-Fi jammers and other signal jamming devices, the agency announced yesterday.

The sale and use of devices that jam the signals of authorised radio communications are illegal in America, the FCC said in its enforcement action. The agency will "vigorously" prosecute violations going forward, it said in a press release.

Public risk

"Our actions should send a strong message to retailers of signal jamming devices that we will not tolerate continued violations of federal law," Michele Ellison, chief of the FCC's enforcement bureau, said in a statement. "Jamming devices pose significant risks to public safety and can have unintended and sometimes dangerous consequences for consumers and first responders."

Jammers, sometimes used in classrooms, theatres and churches, are prohibited because they can prevent individuals from contacting police and fire departments or family members during an emergency, the FCC said. "Use of jamming devices can place you or other people in danger," the agency said.

Disguise

The 20 retailers were marketing more than 200 jamming devices, the FCC said. Among the jammers being sold were GPS blockers for vehicles, high-tech signal blockers with remote control capabilities and jammers disguised as paintings and cigarette packs, the agency said.

The FCC ordered each online retailer to immediately stop marketing signal-jamming devices in the States. If a retailer gets a second citation from the FCC, it could face fines ranging from $16,000 (£12,000) to $112,500 (£84,000), with a separate penalty possible for each device sold or each day a device is marketed, the agency said. Additional violations could result in the seizure of equipment and prison time.