Signedtop plate: GENERAL RADIO CO. (GR logo) FREQUENCY STANDARD / CAMBRIDGE, MASS, U.S.A. / TYPE NO. 1100-A SERIAL NO. 334
plate 2nd from top: CRYSTAL CHECK POINTS FOR / INTERPOLATION OSCILLATOR / (list) / IDENTIFIABLE BY / LOUDEST BEAT TONES / INTERPOLATING / FREQUENCY STANDARD / TYPE NO. 1100-A SERIAL NO. 172 / (GR logo) / GENERAL RADIO CO. / CAMBRIDGE, MASS., U.S.A. / SEE LICENSE NOTICE / U.S. PATENTS / 2,012,497
plate 3rd from top: MULTIVIBRATORS AND / POWER SUPPLY / TYPE NO. 1102-A SERIAL NO. 272 / GR logo) / GENERAL RADIO CO. / CAMBRIDGE, MASS., U.S.A.
bottom plate: PIEZO-ELECTRIC / OSCILLATOR / TYPE NO. 1101-A SERIAL NO. 248 / GR logo) / GENERAL RADIO CO. / CAMBRIDGE, MASS., U.S.A. / SEE LICENSE NOTICE / PATENTS / 1,967,184 1,967,184 2,029,358
face of top meter: (GR logo)
face of bottom meter: WESTON ELECTRICAL INSTRUMENT CORP., MICROAMPERES / A.C. / WESTON / MODEL 506
Inscribedpainted on inside, top panel: LICENSED INSTRUMENT IS LICENSED UNDER / PATENTS OF THE AMERICAN TELEPHONE / AND TELEGRAPH COMPANY SOLELY FOR / UTILIZATION IN RESEARCH, INVESTIGATION, / MEASUREMENT, TESTING, INSTRUCTION / AND DEVELOPEMENT WORK IN PURE / AND APPLIED SCIENCE. / THIS APPARATUS USES INVENSTIONS OF UNITED / STATES PATENTS LICENSED BY RADIO / CORPORATION OF AMERICA. PATENT NUMBERS / SUPPLIED UPON REQUEST. LICENSED ONLY FOR OR / FOR USE IN MEASURING OR TESTING ELECTRONIC / DEVICES, ELECTRON TUBE CIRCUITS, PARTS OF / SUCH DEVICES AND CIRCUITS, AND ELEMENTS / FOR USE IN SUCH DEVICES AND CIRCUITS.
FunctionA frequency standard is an electronic device that generates a signal at a very stable frequency. They are used for controlling the frequencies of radio transmitters, for physical research where a stable frequency source is necessary, and they can be used as a very precise clock.
The type 1100-A, was one of the industry standards, and was built between 1948-1960. Some of them included a clock on its panel (see photograph in reference listed in Primary Sources). Others like this one had a component called the Interpolating Frequency Standard (top on rack) which is used to measure frequencies very accurately.
It was reported to be accurate within 1 part in 10^7 for several months, which was accomplished by keeping the temperature of the oscillating crystal within 0.01°C of a constant.
A quartz crystal frequency standard is one based on the piezoelectric effect. When a piece of crystal is compressed, it generates a voltage, and conversely, when a voltage is applied to a crystal, it compresses or elongates in response. This phenomenon is used to create an electronic circuit in which current and voltage oscillate with a very specific frequency that is given by the size and geometry of the crystal.
Frequency standards based on crystal oscillators were the most accurate form of timekeeping until the development of atomic clocks.
Primary SourcesFor a manual of the Interpolating Frequency Standard component, see The General Radio Experimenter Vol.23, No.7 (Dec. 1948), pp.1-8. Available online here.
ProvenanceCruft?
Related WorksThe model 1100-A frequency standard is described (with a photograph) in:
Marvin E. Frerking, "Fifty Years of Progress in Quartz Crystal Frequency Standards", in 1996 IEEE International Frequency Control Symposium (IEEE, 1996), pp.33-46.