His company $500 million richer and a partnership with Microsoft in hand, Teligent chief executive Alex J. Mandl awoke yesterday feeling secure about the future of his fast-growing competitive local telephone venture.

"When you're building out a large network that costs billions of dollars, it requires capital," Mandl said in an interview. "This is about partnering up with one of the world's greatest companies to help us deliver products to customers faster and better and help accelerate our push into the data world."

The deal announced yesterday brings Vienna-based Teligent $200 million apiece from Microsoft and the investment firm Hicks, Muse, Tate & Furst Inc. Another $100 million comes from three other investment firms. The partnership now claims a 14 percent stake in Teligent.

Wall Street shared in Mandl's enthusiasm: Teligent's shares gained more than a third, closing at $63.87 1/2 yesterday.

The deal hands the company funds to expand into new markets, both domestic and abroad. "This probably pushes their funding requirements out to mid- or late 2001," said Bo Fifer, a telecommunications analyst with Deutsche Banc Alex. Brown in New York.

Not least, it gives the company the imprimatur of stability. "You essentially have Microsoft, one of the biggest, if not the biggest, provider of data services to the residential and business markets essentially putting its stamp of approval on the company," said John Hodulik, an analyst with PaineWebber Inc. in New York.

The key phrase--"data services"--is the buzz word of the moment. For years, telecommunications companies have cashed in on old-fashioned voice calls. These days, as the Internet and electronic commerce explode, the new fight is over fast-moving flows of computer data, or "broadband."

Teligent has grown by claiming small and medium-size business customers and erecting rooftop antennas to transmit calls, bypassing local phone systems. But Teligent sees its future tied to broadband.

Microsoft has been seeking to claim a piece of broadband as well. In May, the company bought a $5 billion stake in AT&T Corp., which plans to sell high-speed Internet access over cable lines. Now, Microsoft is hoping to connect to more customers by way of Teligent's antennas.

That Microsoft chose Teligent is not hard to fathom. Hodulik, the PaineWebber analyst, foresees Teligent growing by 400 percent next year and 150 percent in 2001. But personal history, and Teligent's special pedigree, also explain the connection.

Mandl, the Teligent chief executive, formerly headed AT&T. Liberty Media Group, headed by cable baron John Malone, owns more than 40 percent of the company.

In 1993, Mandl persuaded cellular pioneer Craig McCaw to sell his McCaw Cellular Communications Corp. empire to AT&T for $11.5 billion. McCaw introduced him to Microsoft chairman Bill Gates. The relationship stuck, evolving into one Mandl calls "casual."

As Teligent sought ways to raise capital this year, Mandl said, "Microsoft was just on our list." An approach from Teligent led to several weeks of discussions and, Thursday night, a deal.

Mandl said the company now has the resources to continue building. But with plans to expand in more American cities, and ventures in Hong Kong and Germany, he expects to go to the well again.

"We're not sitting on the edge of our chair worrying about where our capital comes from," Mandl said, "but we'll clearly be looking to raise some more."