of output signals having opposite states q and q which change state each time the output of the proportional controller 26 passes through zero the braking threshold circuit 34 may be a zero crossing detector the output signal q is applied by line 36 to the data input of the flip flop 32 the output from the flip flop 32 can be high as long as q is high the output of the clock 30 clocks the flip flop circuit 32 the output signal from the pulse width control 28 determines the point at which the power signal is reset during each cycle of the clock signal as described below the output drive signal from the flip flop circuit 32 is continually 34 on 34 for fuel flow demand signals which specify a maximum increase in the rate of fuel to be delivered when the output q from the braking threshold circuit 34 is high the duration of the individual pulses outputted by the flip flop 32 is proportional to the duration of the pulses outputted by the pulse width control 28 the duration of each pulse outputted by the pulse width control is equal to the time between the output pulse from the clock 30 going high and the output of the pulse from the pulse width control 28 going high the braking function of the invention is produced by the following elements of fig2 for all rates of decrease in the rate of delivery of fuel greater than the predetermined rate of decrease fig4 line segment cd the pulse width control 40 outputs pulses having a width directly.