Diesel generator speed protection circuit

In the figure, Ai~A4 are T084 four operational amplifiers; SR is a 30:1 variable speed sensor
. The 12V working power supply of the taxi in the circuit is taken from the generator self-starting battery.
  When the generator exceeds the rated speed (set by potentiometer RP2 at 15-60r/min, equivalent to 52H:), the output of A3
to the positive level is higher than the potential of the inverting terminal of A, causing At to flip. The high level passes through Resistor R1. , the diode VD4 reverses
to self-maintain the non-inverting terminal, the transistor VTz conducts, the relay KA is powered on, and the speed-regulating reversible
motor on the generator starts, driving the pull rod to quickly close the throttle and force the engine to stop. When the generator speed drops to a certain level, you can
press the "reset" button SBz to eliminate the self-holding voltage and prevent the unit from starting repeatedly. SB. It is a manual "emergency stop
" button.