Testing of CSM 012 at Downey, Calif., and KSC revealed numerous failures in the communications cable assembly caused by broken wiring, bent pins, and connector malfunctions.

Certain design deficiencies in the system had been remedied by adding adapter cables in series with the cobra cable, but these additions had resulted in additional weak points in the system and in an unacceptably cumbersome cable assembly connected to crew members. For these reasons, Donald K. Slayton, Director of Flight Crew Operations, ruled the existing communications assembly unsafe for flight and requested that the biomedical tee adapter, cobra cable, sleep adapter, and noise eliminator be combined into one new cobra cable for CSM 012.