Privately held Continental Cablevision Inc., the nation’s third-largest cable operator, said its revenues for the year ended Dec. 31 were $ 1.2 billion, a 5.7 % increase from 1992.Operating income before depreciation and amortization was also up 8% to $ 27. 6 million compared to last year, while the cabler’s total debt load was up slightly from $ 3 billion to about $ 3.2 billion. Continental’s capital expenditures rose by almost 28% to $ 185.7 million, a result of rebuilding systems to expand channel capacity and to further deploy new technology. Total number of basic subscribers grew 1.4%, from 2,876,000 in 1992 to 2,915, 000 in 1993. Continental said its interest expense fell 4.4% in the latest year, to $ 276, 698,000, as a result of lower effective interest rates.