"Benjamin F. Husten (left) and Emory D. Heberling (right) of the National Bureau of Standards Central Radio Propagation Laboratory, Microwave Standards section, are shown making adjustments to the amplifier and power supply circuits of NBS's first atomic clock, an ammonia molecule clock developed by NBS from 1948-1949. The amount of equipment shown is larger than needed for the clock alone since some of the instruments are for measurements and performance tests. The circuits essential to the operation of this atomic clock could be condensed into one of the two cabinet racks. Circa 1949." (NIST Digital Archives)