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BELL SYSTEM TECHNICAL JOURNAL 



and at the same time to prevent any lateral movement which would 

 cause a change in the crystal frequency. The crystal and its holder 

 are mounted in an oven fitted with an improved thermostat capable of 

 maintaining the temperature of the crystal constant within extremely 

 narrow limits. This constant temperature oven is built as an integral 

 part of the oscillator, which has been designed to work the crystal 

 under the conditions of optimum stability. 



The oscillator and crystal are carefully shielded and isolated from 

 the output stage by several buffer stages in order to prevent any change 

 in the load conditions from being reflected back to the oscillator and 

 thereby changing its frequency. Careful tests in the laboratory have 

 shown that the output power could be varied from zero to full load 

 without affecting the frequency within the limits of observation, which 



Fig. 4 — Rear view showing interior of oscillator-amplifier unit. 



