This is a negative feedback system, in which the constantly maintained variable is the alternator voltage output. This voltage, after adequate conditioning, is compared with a signal that is stabilised in voltage, temperature and age. The result is an error signal which, when opportunely amplified and compensated, produces a control level that enters an impulse width modulator.

The output of this modulator pulses an SCR with continuous excitation voltage produces in conjunction with, undergoing electromagnetic conversion by generator operation, transforms into generator output voltage. The value of this size is controlled by the "sensing" block.