NEW YORK (AP) _ Teradyne Inc., the largest maker of semiconductor testing equipment, announced Thursday it will buy competitor GenRad Inc. for about $175 million in stock.

The deal also includes the assumption of about $85 million in GenRad debt before considering proceeds from the anticipated sale of a GenRad business unit, which is expected to occur before the merger is completed. GenRad, with headquarters in Westford, Mass., makes electronic test equipment and related software.

The acquisition is expected to be completed in the fourth quarter pending approval by shareholders and regulators.

Under terms of the deal, each GenRad share will be converted into .1733 Teradyne shares.

The deal was announced four months after Boston-based Teradyne said it laid off 650 workers because of slowing worldwide demand for its products. Other cost-cutting measures included furloughs, salary cuts for senior managers and a delay in salary increases for all workers.

Teradyne employs about 10,000 worldwide, and has operations in California, Europe and Asia. About 4,500 of those workers are based in Boston, and Nashua, N.H. GenRad has about 1,300 employees.

GenRad shares soared $1.99, or 50 percent, to close at $5.99 Thursday on the New York Stock Exchange, while Teradyne shares rose 76 cents to close at $35.86.

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On the Net:

Teradyne: http://www.teradyne.com

GenRad: http://www.genrad.com