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BELL SYSTEM TECHNICAL JOURNAL 



Fig. 4 — Experimental bridge stabilized oscillator without provision 

 for temperature control. 



Figure 5 shows the resistance of the lamp Ri plotted against the 

 power dissipated in its filament. The large rise in resistance for small 

 amounts of power is due to the effective thermal insulation provided 

 by the vacuum surrounding the filament and to low heat loss by radia- 

 tion. The lamp operates at temperatures below its glow point, assur- 

 ing an extremely long life for the filament. 



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POWER INTO LAMP IN MILLIWATTS 



Fig. 5 — Characteristic of lamp used for R\. 



