HP Time and Frequency Rack

	HP 113AR Analog Clock -- A precision analog clock/divider that derives its time display from a stable frequency reference. The 113AR divides a high-frequency input signal down to drive clock hands, providing a time display that is directly traceable to the frequency standard.
	Astro Data Precision Time and Frequency Standard -- A time code generator that produces standardized time codes (such as IRIG-B) from a precision frequency reference. Time code generators are essential for applications requiring synchronized timing signals, including military systems, broadcast stations, and scientific instrumentation.
	Collins R-390/URR HF Receiver with matching SSB Unit -- One of the finest communications receivers ever built, the R-390A was designed for the U.S. military in the 1950s. In this time and frequency application, it is used to receive time signals from stations like WWV (Fort Collins, Colorado) on 2.5, 5, 10, 15, and 20 MHz, providing an independent time reference against which local clocks can be compared.
	House Standard: HP 5061A Cesium Beam Frequency Standard -- The cesium beam frequency standard is the most accurate timekeeping device in this collection. It uses the natural resonance frequency of cesium-133 atoms (9,192,631,770 Hz) to produce a frequency output that is accurate to parts in 10¹² or better. This instrument serves as the "house standard" against which all other frequency sources and clocks in the collection are measured. The cesium standard is the same type of technology used in national time standards laboratories worldwide.
	One Second Pulse -- WWV -- An oscilloscope display showing the one-second timing pulse received from radio station WWV. These pulses are broadcast continuously and can be used to check the accuracy of local clocks and frequency standards.
	One Minute Pulse -- WWV -- An oscilloscope display showing the one-minute timing marker from WWV. The minute marker is a longer tone than the second markers, making it easily identifiable for time comparisons.

The Equipment Rack

Top to Bottom:

HP 120AR Oscilloscope
HP Frequency Counter
HP 113AR Analog Clock/Divider
AstroData Frequency Time Code Generator
HP Frequency Counter
HP 5100B/6110B Frequency Synthesizer
HP 5061 Cesium Beam Frequency Standard

Equipment rack contents:

Bottom row (left to right): Pulse generator (214A), long wave receiver, short wave receiver (Collins R-390/A), SSB and fax receivers, radio controlled clock with a Parallax BS2 stamp processor and WWVB receiver.
Upper shelf (left to right): Frequency synthesizer (HP 5100B/6110B) and frequency oscillator, Quartz standard (Frequency Electronics), Loran C/WWVB/WWV time comparators, WWV receivers, Frequency counter (HP 5360A), Biomation memory unit, HP display, AstroData Time Code Generator, and HP 5061 cesium beam frequency standard.

About This Equipment

The instruments shown here represent the precision measurement side of time distribution. While the master clocks in this collection demonstrate how time was displayed and distributed, this equipment demonstrates how time is measured, generated, and verified.

The hierarchy of accuracy runs from the HP 5061A cesium beam frequency standard at the top -- providing the ultimate reference -- through GPS-disciplined oscillators, quartz standards, and frequency counters, down to the WWV radio receivers that provide an independent check against the national time standard broadcast from Fort Collins, Colorado.

Together, these instruments form a complete time and frequency measurement laboratory capable of characterizing any clock or oscillator to extraordinary precision.