Figure 5-15.  Cartridge/pneumatic starter schematic.  Figure 5-16.  Typical starter generator. Figure 5-17.  Starter generator internal circuit.  5-11 The starter generator internal circuit has four field windings:  a series field (C field), a shunt field, a compensating field,  and an interpole or commutating winding.  [Figure 5-17] During starting, the C field, compensating, and commutating  windings are used. The unit is similar to a direct cranking  Relief valve Turbine exhaust ring Overrunning sprag clutch Hot gas nozzles Turbine rotor Gear shaft Compressed air inlet Spline shaft Exhaust from turbine and fan Breech cap Breech handle Switch Flyweight Cartridge Switch  actuating rod Gear ratio approximately 435 to 1 Cooling air To voltage regulator Output To generator paralleling and  protective  circuitry Shunt Series D B + C + A + E Commutating Compensated field Shunt field C field