Within three years, Fairfax County's 250,000 cable television subscribers will no longer need a set-top converter box to view most channels, officials with Cox Communications said yesterday, and that promise led county supervisors to unanimously approve Cox's $1.4 billion purchase of Media General Cable of Fairfax.

Under federal and local law, the buyout of the county's cable TV operator could not take place without the supervisors' approval.

The board had postponed its vote three times in six months while pressing Cox to commit to fixing technical problems that now prevent subscribers from watching channels without a converter box. The converter box makes it impossible to use many advanced features of television sets, such as the ability to tape one program while watching another.

At yesterday's board meeting, company officials said customers will receive TV signals over a single cable--rather than the two cables that now go into each home--by June 2002. Along with other technical changes, the single cable will enable customers to view everything except premium channels without a converter box.

Several supervisors said they were satisfied with the company's action. "The decision to go to a single cable is a tremendous step forward," said Supervisor Stuart Mendelsohn (R-Dranesville). "While it may not happen tomorrow, clearly, in the next couple of years, people are going to have a much better system."

Cox officials said they will also meet with several apartment building owners in Fairfax who have complained that they are trapped in unfavorable long-term contracts with Media General. Several supervisors had urged the cable company to renegotiate those contracts.

But Cox officials declined to roll back a recent rate increase, something that several supervisors had said would endear the new cable company to county residents. "I regret that Cox chose not to seize on that as a piece of consumer goodwill and roll those back," said Supervisor Gerald E. Connolly (D-Providence).

Cox Senior Vice President Claus Kroeger said the system's customers will begin to notice minor changes soon, including new ads for Cox Cable. Technical improvements will take longer, he said.

"I think the supervisors will be pleased with the system we put in place," Kroeger said.