level of the control voltage 110 i e in less than 1 second the oscillator control transistor 81 in addition to having its base electrode biased by the control voltage 110 has v bias voltage applied to its emitter electrode through resistor 89 in the oscillator 80 the transistor 82 operates as the active element which provides the gain necessary to sustain oscillations therein while the transistor 81 operates as a variable resistor which controls oscillator level to maintain operation in the linear mode the capacitors 84 85 operate as a capacitive voltage divider which provides positive feedback to start and sustain oscillations the resistor 89 operates as a minimum control resistance to prevent oscillator instability while the resistor 88 prevents overdriving or damage to the oscillator transistor 82 which could be caused by any radio frequency noise the parallel connected resistor 87 and capacitor 83 provide a bypass circuit for the base electrode of the transistor 82 and generates a turn on bias for the transistor 82 the capacitor 86 operates as a supply voltage bypass and also provides a portion of the oscillator tank circuit the tank circuit of the oscillator 80 is formed by the inductive pickup 40 connected between terminal 43 and ground and the capacitors 84 86 the oscillator 80 generates oscillations in its tank circuit at a carrier frequency of approximately 500 khz and this carrier signal is amplitude modulated by the varying flux loss experienced by the inductive pickup 40 as a result of the rotation of the distributor cam 19 the amplitude of this modulated carrier output signal thus corresponds to the rotation of the distributor cam 19 and hence corresponds to the movements of the associated engine the amplitude modulated oscillator output.