The two agents had the use of the advanced alien technology of their far-off hidden base world. Their headquarters was hidden in Apt. 12-B, 811 East 68th Street in New York City's Upper East Side. They hired Roberta Lincoln as a secretary, telling her that she would be helping their "research for a new encyclopedia".
347 and 201 were both killed in an automobile accident in early 1968. When contact was lost, their supervisor transported himself the 1,000 light years to Earth and saw their mission through. (TOS: "Assignment: Earth")