Sony Corp. yesterday startled the electronics industry with an announcement that it will reverse its iron-clad policy of more than a decade and begin selling VHS video equipment.

Industry analysts said the move was an attempt by Sony to cut losses on what may be the worst failure of its otherwise exemplary corporate history: its uncompromising commitment to the losing Beta format.

Sony denied that the decision would lessen its interest in Beta, which it developed in the early 1970s as the first mass-marketed home video system and has clung to doggedly as VHS battered its market share down to a tiny fraction in the United States and Japan.

Some analysts said Sony's step would push Beta further toward total extinction in the United States. Others, however, discounted that, saying Beta will survive for the foreseeable future in this country. It is often the format of choice for "videophiles" who spend thousands of dollars on their systems, they pointed out. It is also favored by people who bought Beta early on and have built up a tape library.

Sony played down the importance of the move. "All we're doing is diversifying our lineup," said Steve Burke, a spokesman for Sony Corp. of America, the company's U.S. affiliate. "We're not taking any emphasis away from Beta."

Plans call for VHS home video decks initially to be made for Sony on contract by Hitachi Ltd. of Japan. They are to go on sale in Europe this spring, and will be introduced later in the year in the United States.

Still, outside analysts saw the move as a stunning reversal of the set-in-stone Sony position that VHS is a technically inferior system that is not fit to bear the company's label. "This goes against everything that Sony has historically stood for," said James Lardner, author of a book on the industry, "Fast Forward: Hollywood, the Japanese and the VCR Wars."

The move seemed to be another step in Sony's shift from its strategy as an industry maverick interested only in pioneering new products and making everything itself. Sony has now entered the business of making equipment that bears other companies' labels and is farming out some of its production. It is making inroads into the Japanese stereo market by making gear intended to look like everyone else's.

Bob Gerson, editorial director of Twice magazine, a weekly journal of the consumer electronics industry, said Sony's new pragmatism on VCRs will have some immediate payoffs. "There is in this country a Sony customer," Gerson said. "He won't buy anything unless there's Sony on it. So Sony is going to instantly pick up a significant share of the {VHS} market."

Sony engineers developed Beta in the early 1970s, finding ways to use more efficiently the space on half-inch magnetic tape. The name Beta is drawn from the Greek letter and from a Japanese word for a brush stroke in calligraphy that is full and rich, with no white marks in between. It was introduced in the United States in late 1975. VHS is another format that uses half-inch tape but has a larger cassette.

Despite its head start and the prestige of the company behind it, Beta had been overtaken by the late 1970s by the VHS system developed by Japan Victor Co. (JVC). JVC put together a heavyweight coalition of manufacturers for its system, including Japan's dominant electronics producer, Matsushita. RCA's selection of VHS further solidified the format's position in the U.S. market.

A traditional rivalry between Sony and Matsushita played a role in Beta's troubles, analysts say. So did Sony's miscalculation that one hour of playing time, geared to taping TV shows, would be sufficient for home use. VHS first came out with a two-hour duration, making it suitable for the prerecorded movies that are now a multibillion-dollar industry.

Throughout Beta's decline, Sony has refused to throw in the towel in the United States or Japan and switch to VHS. Chairman Akio Morita and other senior executives at Sony continued to preach that the world would sooner or later recognize Beta's technical superiority and bring it to its rightful dominance. One small concession to the reality, however, was that Sony began selling VHS cassettes in 1983.

In 1985, Sony, along with most of the other big electronics companies of Japan, came out with an entirely new -- and standardized -- video format, 8mm. Analysts at that time said this might provide Sony with an honorable exit from its Beta dilemma, assuming that this format took hold and eventually replaced both Beta and VHS.

While 8mm has done well in home cameras, taking about a third of new sales in this country, it has hardly started at all in home decks and prerecorded tapes. "They had hoped it would be much further along than it is," says Eugene Glazer, technology analyst at Dean Witter Reynolds.

The dominance of VHS has continued to grow, with increasing numbers of video rental stores dropping Beta cassettes from their shelves altogether. The video rental chain Erol's Inc. puts only VHS in its new stores, and as a result 43 of its 137 outlets are without Beta, "simply because there isn't the demand," says chain spokesman Vans Stevenson.