#relay box

Astronauts Replace Backup Computer During Spacewalk Outside the International Space Station, Expedition 39 Flight Engineers Rick Mastracchio and Steve Swanson of NASA conducted a spacewalk April 23 to replace a backup computer relay box on the station's S0 (s-zero) truss. The relay box, which failed April 11, is called a multiplexer-demultiplexer, and assists in providing insight and commanding for the station's truss systems and associated hardware.