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Detail of some of pneumatic lines leading into the J-2.

The line toward the left with the labels read "Compressed Gas", "Helium", "1000 PSI", and have arrows pointing into the engine; this is presumably the fill line for the helium tank inside the start tank, used for engine pneumatic control.

The line toward the right with the labels read "Compressed Gas", "Helium", "1250 PSI", and have arrows pointing into the engine; this is presumably the fill line for the start tank, used to start spinning the engine's turbines on the turbopumps.