1390815 Power oscillators STANDARD TELEPHONES & CABLES Ltd 9 May 1972 21577/72 Heading H3F A power oscillator suitable for high frequency heating installations comprises a magnetically focused power valve 1, a tank circuit L 3 , C 3 , and an auxiliary control device 2 arranged in response to an applied control signal to clip the positive peaks of the feedback waveform to the control electrode in a proportionate manner for controlling the power output of the oscillator. The auxiliary control device 2 may be a diode, triode, tetrode or even a transistor (Figs. 1, 2, 4b, not shown), to which an adjustable control signal is applied to render it conducting for a given value of the control electrode voltage. The anode voltage swing is reduced once the device 2 starts conducting and the system finally settles down to a new set of stable conditions with a reduced output power. The control device 2 may be formed separately or enclosed in the same envelope as valve 1.
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