Digital Equipment Corp., in a widely expected move, said it is selling its troubled computer-networking hardware business to Cabletron Systems Inc. for $430 million in cash, stock and product credits. The deal, expected to receive government approval in 60 days, means Maynard, Mass.-based DEC will get $90 million in cash, $50 million in Cabletron stock and $290 million in product credit over the next three years. In return, Cabletron will acquire 250 patents; 900 workers, half of whom are engineers; and a commitment from DEC to generate $1 billion in revenue over the next 3 1/2 years. . . . Ritz Camera Centers Inc. of Beltsville, Md., the nation's largest specialty photography retail chain, has purchased Kits Camera Inc., a 140-store chain based in Seattle, for undisclosed terms.