~(87)Rb atomic frequency standard

ammonium molecular beam frequency standard

atomic beam frequency standard

atomic frequency standard

BSF Basic Standard Frequency

cesium atomic beam frequency standard

Cesium Beam Frequency Standard

cesium fountain frequency standard

crystal-controlled secondary standard frequency measuring equipment

frequency standard

Frequency standard comparison

FS Frequency Standard

Hydrogen Frequency Standard

hydrogen maser frequency standard

Locked - phase standard frequency source

locked-phase standard frequency source

medium standard frequency

primary frequency standard

quantum frequency standard