South Carolina's proposal to jam cell phone signals in prisons violates federal law, but regulators said Thursday they are willing to work with officials in their efforts to keep inmates from making calls using the contraband devices.

State prisons chief Jon Ozmint wants to demonstrate how the jamming technology would work. Federal Communications Commission spokesman Robert Kenney said the agency recognizes officials' distress about contraband cell phones, which some say have become a new form of cash behind bars.

"We understand public safety's concerns and are willing to work with them going forward," Kenney said.

The FCC can grant federal agencies the authority to use the jammers, which prevent cell tower signals from ever reaching a phone, effectively blocking all calls. But there's no such provision for state and local law enforcement, and Ozmint has invited a company that sells the equipment to demonstrate it next week at a South Carolina prison.

Experts say the consequences of not using jammers can be dire. Ozmint blames illegal cell phones for most escapes from South Carolina prisons. And last summer in Maryland, Baltimore resident Carl Lackl was gunned down outside his home after authorities say a shooting suspect he identified ordered a hit on him from behind bars.

In Texas last month, prison officials arrested the mother of a death row inmate on charges she paid for minutes on a cell phone that had been smuggled to her condemned son. Authorities said the inmate shared the phone with nine other inmates and called a state senator to say he knew the lawmaker's daughters' names.

Critics say it's impossible to contain the jamming technology to one or two buildings, and that using it runs the risk of affecting people using phones nearby. On Wednesday, Steve Largent, president of wireless industry trade group CTIA-The Wireless Association, called on the FCC to enforce the ban and stop the demonstration in South Carolina.

"I hope you are disturbed as much as I am that CellAntenna would so brazenly violate federal law, especially where there are lawful alternatives to combating contraband in prisons," wrote Largent, formerly an Oklahoma congressman and wide receiver for the NFL's Seattle Seahawks. "I hope you will enforce the federal ban on the sale or use of wireless jammers by directing the FCC Enforcement Bureau to issue an order ... directing parties involved not to conduct the demonstration and/or ask the United States Department of Justice ... to file suit in federal court to enjoin the demonstration."

South Carolina prisons officials say they're already using alternative methods like scanners and searches that comply with the Commission's rules, but cell phones still get in.

"As long as you have human beings in prisons as inmates and employees, and as long as there are human beings on the outside of those prisons, you're going to have contraband in prison," Ozmint said last month. "This is a threat that can be absolutely eliminated."

Members of South Carolina's Congressional delegation, law enforcement officials and the FCC have been invited to next week's demonstration. Kenney said FCC officials have not decided if they will send a representative.