21. On 15 February the new Semi Automatic Ground Environment ( SAGE ) Direction Center ( DC-16 ) became operational. 22. Most models have 6-speed manual transmissions; whilst a smaller number of other models use the semi automatic Selespeed system. 23. On 15 November 1959, the new Semi Automatic Ground Environment ( SAGE ) Direction Center ( DC-10 ) became operational. 24. On 1 March 1959 the new Semi Automatic Ground Environment ( SAGE ) Direction Center ( DC-05 ) became operational. 25. On 1 February 1959 the new Semi Automatic Ground Environment ( SAGE ) Direction Center ( DC-04 ) became operational. 26. On 1 December 1961, the new Semi Automatic Ground Environment ( SAGE ) Direction Center ( DC-22 ) became operational. 27. On 15 November 1959, the new Semi Automatic Ground Environment ( SAGE ) Direction Center ( DC-11 ) became operational. 28. This version of the aircraft was extensively used within the Semi Automatic Ground Environment ( SAGE ) air defense system. 29. On 1 December 1960 the new Semi Automatic Ground Environment ( SAGE ) Direction Center ( DC-18 ) became operational. 30. On 15 February 1960 the new Semi Automatic Ground Environment ( SAGE ) Direction Center ( DC-20 ) became operational.
