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BELL SYSTEM TECHNICAL JOURNAL 



not involving a rotating machine in the control system, was suggested and 

 the first quartz crystal clock was constructed using the simpler means. 

 This apparatus was described by Horton and Marrison^*^ before the Interna- 

 tional Union of Scientific Radio Telegraphy in October, 1927. The reso- 



Fig. 10 — 50,000-C3cle quartz resonator, in original mounting, used in first quartz 

 clock— 1927. 



-JS^" 



HIGH-FREQ. a; 

 INPUT 



CONTROLLED 



LOW-FREQ. 



OUTPUT 



Fig. 11 — Submultiple controlled frequency generator used in first quartz clock. 



nator in its mounting that was used in this first model is shown in Fig. 10. 

 It consisted of a rectangular block of crystal, cut in the manner usually 

 called X-cut, and of such size as to oscillate at a frequency of 50,0(X) cycles 

 I>er second in the direction of its length. The temperature coefiicient of 

 this resonator was approximately 4 parts in a million per degree C at the 



