piezoelectric oscillator, type 275
Date: ca. 1924-1926
Inventory Number: RS0655
Classification: Frequency Standard
Subject:
Maker: General Radio Company (1915-present)
Maker: Cruft Laboratory, Harvard University (founded 1914)
Maker: George Washington Pierce (1872 - 1956)
Maker: (meter) Weston Electrical Instrument Corporation (founded 1888)
Maker: (batteries) Burgess Battery Company (founded 1917)
Cultural Region:
City of Use:
Dimensions:
20 x 24 x 12 cm (7 7/8 x 9 7/16 x 4 3/4 in.)
Accessories: crystal unit; removable coil; 3 (?) batteries (removed during FAE inventory).
Description:
Square wooden box with leather handle on top and black front panel. On the panel there is a circular window with a milliammeter (arched scale with arrow-shaped needle), two dials (one with knob missing) and 4 pairs of connectors to plug in electronic components as following: two pairs on top left labelled "CRYSTAL" (both), "H.F." (top) and "L.F." (bottom); one pair on top right labelled "COUPLING COIL"; one pair on bottom left labelled: T[EL?]
Top of box is a hinged lid. Inside are batteries (now removed) and electronic parts. A hand-drawn circuit diagram is taped on the inside of the lid.
It includes two components to plug to the front panel: a coil (probably the "coupling coil") and the crystal unit, a flat metal cylindrical unit embedded in a square insulating frame.
Top of box is a hinged lid. Inside are batteries (now removed) and electronic parts. A hand-drawn circuit diagram is taped on the inside of the lid.
It includes two components to plug to the front panel: a coil (probably the "coupling coil") and the crystal unit, a flat metal cylindrical unit embedded in a square insulating frame.
Signedetched and white filled on front panel, lower left: PIEZO-ELECTRIC OSCILLATOR / TYPE 275 SERIAL NO. 16 / GENERAL RADIO CO. / CAMBRIDGE, MASS.
on crystal unit: CRUFT LAB / CRYSTAL No. 221 / W.L. 281.5 / 260.4
on face of meter: WESTON MILLIAMMETER / WESTON ELECTRICAL INSTRUMENT CO., NEWARK, N.J., U.S.A. / MODEL 301 NO. 222311
on batteries (now removed): BURGESS / BATTERY / COMPANY
on crystal unit: CRUFT LAB / CRYSTAL No. 221 / W.L. 281.5 / 260.4
on face of meter: WESTON MILLIAMMETER / WESTON ELECTRICAL INSTRUMENT CO., NEWARK, N.J., U.S.A. / MODEL 301 NO. 222311
on batteries (now removed): BURGESS / BATTERY / COMPANY
Inscribedblack painted on lid: CRUFT / INSTRUCTION
FunctionA piezoelectric oscillator is a device that generates a very stable signal at a very precise, specific frequency. It accomplishes this making use of oscillations in a crystal due to the piezoelectric effect. When a crystal is compressed, a voltage forms between its compressed sides, and conversely, if a voltage is applied to a crystal, it compresses or elongates. An electronic circuit can be designed in which the current and voltage oscillate at a very specific frequency determined by the size and geometry of the crystal.
The central element of the oscillator is the small crystal unit, which is plugged into the front panel. It contains a small circular wafer of quartz sandwiched between electric contacts.
The initial concept of the piezoelectric oscillator was created and patented by Walter Guyton Cady, a physicist at Wesleyan University in Connecticut, around 1919-1921. In 1924, George Washington Pierce, Head of the Cruft Laboratory at Harvard, turned this concept into a simple, workable electronic circuit. He understood the importance of a frequency standard in order to make sure that radio broadcasters maintained their assigned frequency accurately at a time when the overcrowding of the aether was a major concern and emission frequencies veered off their assigned slot as they were controlled by simple electronic circuits which were sensitive to changes in temperature and other variables. Pierce's piezoelectric oscillator was an immediate success and was produced by General Radio, licensed by both Pierce and Cady. Soon after, frequency standards like this one were used to build the first form of electronic quartz clock, the most precise timekeeping device of their time.
In the following decade, G.W. Pierce was involved in many patent litigations with AT&T , which was applying for patents based on what Pierce considered his original design and patents. During that time, in addition to defending his claims on the piezoelectric oscillator (finally settled in 1936), Pierce developed an entirely different form of frequency standard, the magnetostriction oscillator. Several examples of magnetostriction oscillators are kept in the Collection: RS0205, RS0342, RS0656, RS1163, RS1275, and RS1313a,b.
The central element of the oscillator is the small crystal unit, which is plugged into the front panel. It contains a small circular wafer of quartz sandwiched between electric contacts.
The initial concept of the piezoelectric oscillator was created and patented by Walter Guyton Cady, a physicist at Wesleyan University in Connecticut, around 1919-1921. In 1924, George Washington Pierce, Head of the Cruft Laboratory at Harvard, turned this concept into a simple, workable electronic circuit. He understood the importance of a frequency standard in order to make sure that radio broadcasters maintained their assigned frequency accurately at a time when the overcrowding of the aether was a major concern and emission frequencies veered off their assigned slot as they were controlled by simple electronic circuits which were sensitive to changes in temperature and other variables. Pierce's piezoelectric oscillator was an immediate success and was produced by General Radio, licensed by both Pierce and Cady. Soon after, frequency standards like this one were used to build the first form of electronic quartz clock, the most precise timekeeping device of their time.
In the following decade, G.W. Pierce was involved in many patent litigations with AT&T , which was applying for patents based on what Pierce considered his original design and patents. During that time, in addition to defending his claims on the piezoelectric oscillator (finally settled in 1936), Pierce developed an entirely different form of frequency standard, the magnetostriction oscillator. Several examples of magnetostriction oscillators are kept in the Collection: RS0205, RS0342, RS0656, RS1163, RS1275, and RS1313a,b.
Historical AttributesInscriptions and painted triangle indicate that it was later used for instruction in the Cruft Laboratory, Physics Department, Harvard University.
Curatorial RemarksBatteries removed.
There are three similar piezoelectric oscillators in the Collection: RS0655, RS1292, and RS1441.
There also exists in the Collection a more recent General Radio frequency standard: RS0098.
There are three similar piezoelectric oscillators in the Collection: RS0655, RS1292, and RS1441.
There also exists in the Collection a more recent General Radio frequency standard: RS0098.
ProvenanceCruft Laboratory, Department of Physics, Harvard University.
Published ReferencesFor a detailed history of the development of the crystal oscillator including George Washington Pierce's contributions, see:
Christopher Shawn McGahey, Harnessing Nature's Timekeeper: A History of the Piezoelectric Quartz Technological Community (1880-1959) . Ph.D. Dissertation (History, Technology and Society), Georgia Institute of Technology (2009).
Available online at the IEEE Ultrasonics, Ferroelectrics and Frequency Control Society here.
The photograph of a very similar crystal unit is on page 186.
For more details on the patent litigations related to Pierce's piezoelectric oscillators, see:
Karl D. Stephan, A Texan at Harvard: Did success spoil George Washington Pierce? . Available at The University of Texas - Austin's TxTell website here.