NEW YORK -- Xerox Corp. plans to unveil today a product it calls its most important development since it introduced the modern copying machine 31 years ago.

The new device is a combination copier, fax, image scanner and document printer designed to tie together those now-separate operations at large companies.

Using the machine, a worker could push a button on his or her desktop computer and order up one -- or several hundred -- high-quality, bound copies of a 50-page report. A worker also could send a fax of a computer document to another computer user, industry analysts said.

In addition, the machine could electronically "scan in" paper documents that then could be stored in a computer or manipulated on a computer screen.

"It's really meant to bring the copier into the computer network," said Ann Palermo, an analyst at the market research firm International Data Corp.

The device is considered a gamble by Xerox, which has been disappointed in the past by making technological breakthroughs only to lose the market for them to other companies.

"They have spent a fortune on the development of this system," said Eugene Glazer, an analyst at Dean Witter Reynolds Inc. He said the research cost ran into the hundreds of millions of dollars. "The people that have seen it are very impressed," he said. But, he added, the market potential for the device -- expected to cost at least $200,000 -- is uncertain.

"They're trying to create a market, and the question is, can they create it at that price," said Peter Enderlin, an analyst at Smith Barney, Harris Upham and Co.

Added Glazer, "They'll be introducing it into a difficult economic environment, where the budgets of potential user organizations will be under constraints."

Xerox wouldn't discuss details of the product, but it called a news conference for today in New York to make what it called its most important announcement since it introduced the automatic, plain paper copier in 1959. It said the announcement is a follow-up to its unveiling last month of a new personal computer and software designed to tie together users throughout a company.

Xerox apparently views the new device as a way for companies to control the proliferation of paper and computer documents. The machine could be another step in the long-promised "paperless" office since it would allow documents to be stored in computers instead of in file cabinets. Such electronic "imaging" systems are offered by other companies but have not yet found a mass market.

Palermo said the new machine, believed to be called the Docutech Publisher, could replace print shops at major companies. She said high-speed printing devices used for high-quality, multiple-copy reproduction cost about $150,000, so the anticipated price of the Xerox machine is not out of line.

Enderlin said investors apparently aren't excited about the announcement. Xerox's stock price has fallen in recent weeks, as has the market in general, since news of the machine began to appear. Xerox stock closed up $2 at $36.25 yesterday in New York Stock Exchange trading.