active element in amplifier being vacuum tube (H03B5/38 takes precedence)

Full Title

Generation of oscillations using amplifier with regenerative feedback from output to input (H03B9/00, H03B15/00 take precedence) > with frequency-determining element being electromechanical resonator > being a piezoelectric resonator (selection of piezoelectric material H10N30/00) > active element in amplifier being vacuum tube (H03B5/38 takes precedence)