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