Tekelec (Nasdaq: TKLC), whose chief executive officer resigned last month, missed Wall Street expectations with a bigger loss than expected in fourth quarter earnings but did hit the high end of its revised revenue projections for 2010.

However, Tekelec also forecast a tough year in 2011 with revenues estimated to be between $360-$400 million. That’s well below 2010’s revenues of $424 million.

Analysts expected revenue of $432.9 million, according to Reuters.

The news sent Tekelec shares down 13 percent, or $1.47, to $10.26. That’s a new 52-week low.

In its announcement, Tekelec noted that “we do not expect to repeat” a $26 million order from a “North American customer” for signaling gear.

In earnings announced early Thursday, the networking equipment and software manufacturer and services provider said it lost $1.2 million, or 2 cents per share, after one-time exceptions in the fourth quarter.

Analysts polled by Thompson Reuters expected a 1-cent loss.

Quarterly revenues plunged to $90.2 million, down 27 percent from a year earlier when Tekelec posted a 23-cent profit.

However, fourth quarter orders did increase to $178.4 million, up 10 percent from the same quarter in 2009 and ranking as the second highest in the firm’s history.

Tekelec closed at $11.73 Wednesday. Its shares had traded north of $13 immediately after changes in management in January but are well off the 52-week high of $19.89 from last spring.

Last month, Frank Plastina left as Tekelec’s CEO and also resigned his board seat. He is to receive a severance package of some $2.5 million. (Read the details here.)

Krish Prabhu, a board member at Tekelec and a veteran telecommunications executive, took over as CEO.

At the time of Plastina’s departure, Tekelec cut its 2010 revenue forecast to between $410-425 million, down from an earlier projection of $430-440 million.

Revenues came in at $424 million, down 10 percent from 2009.

Last November, Tekelec reduced its revenue guidance to $430-$440 million from $430-$450 million.

A delay in a $10 million project in India helped drive down the company’s revenue.

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