536 BELL SYSTEM TECHNICAL JOURNAL 



The significance of the unusually stable properties of quartz crystal — 

 which at times were viewed with a sort of awe and a tendency at first to 

 expect too much^^* — y^^s soon recognized in relation to precise standards 

 of frequency and time, and many laboratories made experiments directed 

 toward these applications. 



For some years these efforts usually took one of two forms: either that of 

 a quartz-controlled oscillator used as a comparison standard by various 

 means^^, or that of using the quartz resonator itself as a portable standard, 

 the high-frequency counterpart of an isolated tuning fork. Probably the 

 most convenient standards of the latter sort were the luminous resonators 

 first described in 1925 by Giebe and Scheibe^^. The following year they 

 proposed the use of such luminous resonators as frequency standards^^ and, 

 shortly following, portable frequency indicators of this sort were made 

 available for general use. The use of such a luminous resonator for the 

 international comparison of frequency standards was reported by S. Jimbo 

 in 1930.^^ The first international comparison of frequency standards 

 making use of piezo resonators as isolated standards was carried out by 

 Walter G. Cady in 1923, who by means of a set of early type resonators com- 

 pared the existing standards at Rome, Livorno, Paris, Teddington, Farn- 

 borough, Washington, and Cruft Laboratory at Harvard University^^. 

 In the following year the U. S. Bureau of Standards carried out a similar 

 international frequency comparison, but of greater accuracy, employing 

 portable quartz crystal oscillators. This comparison and other important 

 related studies were described by J. H. Bellinger in 1928 — ''The Status of 

 Frequency Standardization"^^. 



It was soon recognized that quartz oscillators could be built with a 

 stability far greater than that of any other known type and that they possess 

 qualities very desirable for a combined time and frequency standard. 

 However, all early quartz oscillators had frequencies far too high to operate 

 any synchronous motor and it was not immediately obvious how a clock 

 could be operated thereby. 



The Frequency Divider , • 



The illustration in Fig. 9 from the author's notebook for November, 1924 

 is believed to be among the earliest means proposed to accomplish this. 

 In brief, the proposal was to control the speed of a motor driving a high- 

 frequency generator so that a harmonic of the generator output, say the 



* In 1929, M. G. Siadbei wrote "Nous pensons que le quartz pi6co6Iectrique peut 

 trouver un nouvel emploi dans la chronometrie, 6tant donn6e la conservation rigoureuse- 

 ment constant de ses oscillations." 



"La seul cause de variation de la p^riode d'oscillation r^sulte en effect du changement de 

 la temperature. . . .' 



