A businessman pleaded guilty Friday to selling 20,000 illegal cable television decoders through advertisements in newspapers and national magazines in what federal prosecutors described as one of the largest cable theft schemes ever uncovered.

Arthur Brett Kaufmann, 38, of Livingston, pleaded guilty to mail fraud and income tax evasion in a hearing before U.S. District Judge H. Lee Sarokin.Prosecutors estimated that unauthorized interception of premium cable channels by Kaufmann's customers is costing cable companies $5 million a year.

Kaufmann has been cooperating with the FBI for the past year, testifying at trials in several states and continuing to order equipment as part of an undercover investigation, U.S. Attorney Samuel Alito said.