Shares of

Efficient Networks

(EFNT)

skyrocketed in preopen trading Thursday after the company announced it was being acquired by Germany's

Siemens

(SMAWY)

for about $1.5 billion in cash.

The shares surged $10.81, or 87.4%, to $23.19 in

Instinet

trading, up from Wednesday's close of $12.38 on the

Nasdaq

.

The digital subscriber line, or DSL, equipment maker, which is based in Dallas, said Siemens, an engineering and electronics group, has offered to buy the company for $23.50 a share, or double Wednesday's closing price. Both companies have approved the deal.

"With the strong presence of Siemens ICN in over 160 countries, this acquisition will empower us to further accelerate the growth of our business, and enhance our ability to drive the global adoption of broadband networks and services," said Mark Floyd, Efficient Networks' founder and board chairman.

The company also announced today that it has been selected by

SBC Communications

(SBC)

as its provider of external Ethernet-attached DSL modems for a one-year period. Efficient Networks has been supplying DSL modems to SBC since an initial agreement in October 1999.