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Space shuttle Atlantis astronaut Randy Bresnik works during the second spacewalk of the mission at the International Space Station on Saturday. ((NASA/Associated Press))

Astronauts from space shuttle Atlantis completed the second of three scheduled spacewalks Saturday, spending just over six hours installing equipment on the International Space Station.

Mission specialists Randolph Bresnik and Michael Foreman hooked up new antennas, relocated a monitor, set up an attachment for a spectrometer and installed a wireless video system for spacewalkers' helmet cameras.

The spacewalk was delayed more than an hour by false decompression alarms that sounded late Friday for the second night in a row.

The high-pitched beeps — emanating from a new Russian research chamber — triggered a series of smoke alarms, waking up the astronauts and disrupting spacewalk preparations.

As the astronauts carried out their work, Bresnik's wife, Rebecca, was due to give birth to their second child at any moment in Houston. They also have a three-year-old son, adopted from Ukraine.

However, the baby had yet to arrive by the time the spacewalk ended. It had been agreed that Mission Control would hold off on any news if the birth occurred during the spacewalk so that Bresnik would remain focused on his tasks.

Throughout the spacewalk, Foreman, a veteran spacewalker, had trouble hearing inside his helmet. Bresnik's voice was especially faint.

"I can't understand you," Foreman called out. Bresnik spoke louder. "Still can't," Foreman said. An astronaut inside the space station had to intercede.

Foreman also missed hearing some of the praise coming his way after accomplishing all the major chores.

One more spacewalk is planned on Monday. The shuttle will remain at the station until next Wednesday, with a return to Earth scheduled for Friday.

With files from The Associated Press