582 



BELL SYSTEM TECHNICAL JOURNAL 



25° C 



Pt = WATTS 



Ta=280*' C 



3. Pt= 1.2 WATTS Ta= 382 ° C 4. Pj = 2.1 WATTS Ta=438°C 



Pt = 4.0 WATTS 



Ta=525' 



Pt = 6.0 WATTS 



556°C 



Fig. 78. — A series of x-ray photographs of the thermal tuning mechanism of an operating 

 2K45. These show the motion of the bows for successively increasing power inputs to 

 the tuner channel. 



to sustain /„ . \\'e say that the control is positive if no overshoot occurs, i.e., 

 if the frequency does not continue to change for a time and then return to 



