Auto transformer Input lead Power source Noise filter Breaker Multilobe cam Single-lobe cam Motor Contactor Rectifier Storage capacitor To other exciter Trigger capacitor Triggering transformer Spark igniter Bleeder resistor Figure 4-66.  Capacitor-type ignition system schematic.  against leakage of high-frequency voltage interfering with  the radio reception of the aircraft. spark igniter varies in proportion to the voltage of the DC  power supply that affects the rpm of the motor. However,  since both cams are geared to the same shaft, the storage  capacitor always accumulates its store of energy from the  same number of pulses before discharge. The employment  of the high-frequency triggering transformer, with a low- reactance secondary winding, holds the time duration of the  discharge to a minimum. This concentration of maximum  energy in minimum time achieves an optimum spark for  ignition purposes, capable of blasting carbon deposits and  vaporizing globules of fuel. This capacity-type system provides ignition for turbine  engines. Like other turbine ignition systems, it is required  only for starting the engine; once combustion has begun, the  flame is continuous.  [Figure 4-67]  The energy is stored in capacitors. Each discharge circuit  incorporates two storage capacitors; both are located in the  exciter unit. The voltage across these capacitors is stepped  up by transformer units. At the instant of igniter plug firing,  the resistance of the gap is lowered sufficiently to permit the  larger capacitor to discharge across the gap. The discharge  of the second capacitor is of low-voltage, but of very high  All high-voltage in the triggering circuits is completely  isolated from the primary circuits. The complete exciter is  hermetically sealed, protecting all components from adverse  operating conditions, eliminating the possibility of flashover  at altitude due to pressure change. This also ensures shielding  Capacitor Discharge Exciter Unit 4-41