PSINet Inc. is moving its headquarters from Herndon to Loudoun County, according to spokesman Doug Baj. The company is set to purchase the Alcatel building on Route 7, as well as two adjacent parcels of land on which it plans to build another office building and a facility to house computer servers and equipment.

The deal is still under contract, but PSINet representatives said they expect it to be signed by Feb. 1. Telephone calls to Alcatel U.S.A., which has been downsizing steadily in Loudoun, were not returned.

PSINet would consolidate five facilities now located in Fairfax County and elsewhere in Northern Virginia and bring about 900 employees to Loudoun, although one of the current facilities may remain open.

With MCI WorldCom Inc. and America Online Inc. already in the Dulles area, "this brings what I like to call the `triple crown' of the Internet to Loudoun County," said Robyn Bailey, marketing manager for the Loudoun County Department of Economic Development.

Like its future neighbor MCI WorldCom Inc., PSINet is pushing to become what is known as an "Internet super-carrier." The company, which had 1998 revenue of $259.6 million, announced in October that it would spend $1.4 billion to expand its fiber-optic network.

David Ruppe, director of real estate for PSINet, said the company chose Loudoun because "we wanted to not move far, and we were looking for something that was a good value and convenient to the airport."

Ruppe said many of PSINet's employees already live in the Sterling area, "so we weren't really increasing a lot of people's commute."

Recently, PSINet joined seven other high-tech firms in the region to lobby the Virginia General Assembly in Richmond for tax breaks on equipment for facilities they are building or expanding to house Web servers.

Ruppe said PSINet is still in negotiations with the county to discuss the terms of the move, including any deals the county may have to offer. But so far, the county has not offered anything "out of the ordinary," Ruppe said.

Baj said he did not know where Alcatel plans to move its remaining employees.

The Ashburn division of French-owned Alcatel, which makes the component parts of communication networks, moved to Loudoun in 1996 with 500 employees. The division laid off 140 employees in November 1998 and an additional 150 in April, leaving most of its red brick building empty.

At the time, the future of the division was in question. After former division head Jean-Luc Abaziou left to become head of Torrent Networking Technologies Corp. in Silver Spring, Alcatel appointed a new person to the top job. But in April the company said the division would no longer have a local leader, and instead would fall under the aegis of the president of Alcatel U.S.A.