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 the cathode 14, so that {TAIL ~ an amount} of electron emission is controlled to adjust the tube current 
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 the cathode 14 , so that { TAIL ~ 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 OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH