EVOLUTION OF QUARTZ CRYSTAL CLOCK 



535 



The feedback to sustain oscillations in the electrical circuit could be obtained 

 only through the vibration of the quartz rod and hence was precisely con- 

 trolled by it. Cady's results were received with widespread interest and 

 were duplicated and continued in many laboratories, which soon resulted 

 in many new discoveries and inventions. 



(a) EARLIEST QUARTZ OSCILLATOR, ^ 



WALTER G. CADY, 1921 



(b) PIERCE AND PIERCE -MILLER OSCILLATORS 



(C) BRIDGE STABILIZED OSCILLATOR, L.A.MEACHAM 



Fig. 8 — Typical quartz oscillator circuits. 



Important contributions were made by G. W. Pierce, who, showed in the 

 following year that plates of quartz cut in a certain way could be made to 

 vibrate so as to control frequencies proportional to their thickness®^ He 

 also proposed somewhat simplified circuits for their use which soon found 

 very general appHcation in the construction of wavemeter standards and 

 later for oscillators used to control the frequency of broadcasting stations 

 and for many other purposes. In 1924, the General Radio Company of 

 Cambridge, Massachusetts, produced a commercial instrument based on 

 these studies. 



