Skylab Intercom Speaker and Control Box, measuring 10″ x 13″ x 6.5, with a McDonnell Douglas identification plaque on the side: "Speaker Intercom, Part NO. 61A850003-321, Serial No. 1072." The unit was designed to serve as both a loudspeaker and control box for the Skylab intercom system, featuring a speaker volume knob, intercom and transmit switches, and channel selectors.
The space station was large and had areas that were not easily visible from each other, so the intercom was a valuable system—crewmen could talk to each other or to ground crews from any one of twelve locations. Unaided voice communication between astronauts was difficult because of poor transmissibility caused by low atmospheric pressure in Skylab. Remembering the Skylab 2 mission on its 35th anniversary, Science Pilot Joe Kerwin recalled: 'We'd go off after breakfast in the morning, somebody would go to do Earth resources, somebody would go do solar physics, somebody would be downstairs doing housekeeping and you couldn't even hear or see each other, you'd have to talk on the intercom.'
