The heater 56 has both ends connected to a heater power supply 58 which controls the heating temperature of the heater 56 to regulate {HEAD ~ the temperature} of {TAIL ~ the cathode} 14, so that an amount of electron emission is controlled to adjust the tube current 
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The heater 56 has both ends connected to a heater power supply 58 which controls the heating temperature of the heater 56 to regulate { HEAD ~ the temperature } of { TAIL ~ the cathode } 14 , so that an amount of electron emission is controlled to adjust the tube current
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH