active element in amplifier being vacuum tube

Generation of oscillations using amplifier with regenerative feedback from output to input > with frequency-determining element comprising resistance and either capacitance or inductance, e.g. phase-shift oscillator > the frequency-determining element being part of a bridge circuit in a closed loop in which the signal is transmitted; the frequency-determining element being connected a bridge circuit to such a closed loop, e.g. Wien-Bridge oscillator, parallel-T oscillator > active element in amplifier being vacuum tube

Generation of oscillations using amplifier with regenerative feedback from output to input (H03B9/00, H03B15/00 take precedence) > with frequency-determining element comprising resistance and either capacitance or inductance, e.g. phase-shift oscillator > frequency-determining element being part of bridge circuit in closed ring around which signal is transmitted; frequency-determining element being connected via a bridge circuit to such a closed ring, e.g. Wien-Bridge oscillator, parallel-T oscillator > active element in amplifier being vacuum tube