EVOLUTION OF QUARTZ CRYSTAL CLOCK 



563 



of the Bell System and, through the Long Lines Department, to outside 

 agencies. 



A considerable number of quartz clocks have been built and used in 

 laboratories and observatories all over the world, some as standards of 



Fig. 30 — Clock dial and monitoring equipment associated with the Bell System Fre- 

 quency Standard, 1937 to date. 



frequency, some as precise clocks, and others for general use in all measure- 

 ments of rate and time. It would be impossible to mention all of these, for 

 already there are many of them. But certain installations are of especial 

 interest and will be discussed briefly. 



