Tele-Communications Inc., the nation’s largest cable operator, reported net profits of $ 31 million (7 cents a share) for the second quarter, ended June 30. That compares to a $ 6 million net loss (2 cents) in the same period last year.

Revenues were up substantially, climbing 18.5% to $ 1 billion compared with the comparable quarter.

Operating earnings, before income taxes, more than doubled to $ 52 million from $ 24 million a year earlier.

The results also include a $ 5 million onetime gain from the sale of certain assets, the company said, and a $ 3 million loss from early retirement of debt.

Brendan Clouston, TCI’s chief operating officer, warned investors that sustained profitability could not be guaranteed considering new rate regulations starting in September. “A few weeks ago, we announced that revenue would decrease by $ 140 million to $ 160 million,” the exec said.