A former National Security Agency employee convicted of selling defence and communication secrets he gained during his career to the Soviet Union has been released from US custody 30 years after his arrest. The sentence for Cold war-era spy Ronald Pelton, 74, ended on Tuesday. He had been placed on home confinement several months ago to serve out the final stretch of his sentence and was released on uesday from the custody of the Bureau of Prisons, agency spokesman Ed Ross said. Pelton, a former NSA intelligence communications specialist, was arrested in November 1985 on charges of selling information to the Soviets about signals intelligence between 1980 and 1985 for US$35,000 plus expenses. Prosecutors have said a Soviet KGB agent who defected and later returned to Moscow tipped investigators to Pelton. Among the secrets Pelton gave up was information about Operation Ivy Bells, an effort by the NSA and the Navy to tap Soviet communications cables that were laid under the ocean. He was sentenced to three life terms in 1986 by a federal judge who said he had betrayed a “special position of trust”, compromised citizens of the United States and endangered US agents. Under sentencing rules in place at the time, Pelton was presumptively entitled to release on parole this month after 30 years in custody. Pelton asked for leniency at sentencing, saying that with a lesser sentence, “I could at least make the rest of my life count.” His lawyer called the espionage “the biggest mistake of his life”. Pelton worked for 14 years for the NSA before resigning in 1979. The FBI says Pelton, because of financial problems, approached the Soviet Embassy in Washington after leaving the agency and offered to sell the secrets. The year of Pelton's arrest, 1985, came to be known as the Year of the Spy because of several high-profile espionage cases that occurred then. Among them were Jonathan Pollard, the former Navy intelligence analyst who provided classified information to Israel and was paroled last week after 30 years in custody, and John Anthony Walker Jr., the former US Navy warrant officer who passed cryptographic secrets to the Soviets and died last year. Pelton had served time in a federal prison in Pennsylvania, but was transferred in the last year to a halfway house and then to home confinement, said Ross, the Bureau of Prisons spokesman.