The Hewlett-Packard Model 5061B Cesium Beam Frequency Standard is a compact, self-contained frequency standard which uses a cesium beam tube resonator to stabilize the output frequency of a quartz crystal oscillator. Solid state components and the closed-loop, self-checking control circuit provide excellent accuracy. When the high-performance tube Option 004 is installed in the HP 5061B, accuracy is increased. Available output frequencies are 10 MHz, 5 MHz, 1 MHz, and 100 kHz.