noun
1. : an amplifier tube of extremely high sensitivity used in a vacuum-tube measuring instrument (as a voltmeter)
2. : a vacuum tube having high impedance in the grid circuit so as to minimize the undesirable control-grid current
noun
1. : an amplifier tube of extremely high sensitivity used in a vacuum-tube measuring instrument (as a voltmeter)
2. : a vacuum tube having high impedance in the grid circuit so as to minimize the undesirable control-grid current
Webster's New International English Dictionary. Новый международный словарь английского языка Webster. 2012