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In 1956, Life Magazine(r) ran a full-page photograph of Dudley Buck which illustrated
the difference in size between a typical computer vacuum tube and a cryotron.

This cryotron above has 78 turns for the control winding, approximately 30 mm long.

Close-up view of four cryotrons in a circuit called a 'step oscillator'.  The control coils are wound with 0.003 inch diameter niobium wire.  The gate wire is tantalum.