Sequential parking circuit for two electric motors

In some working procedures, the first motor is required to stop before the other one is allowed to stop. The figure below shows the circuit adapted to this operating procedure. When the ST1 start button is pressed, the motor M1 runs; then ST2 is pressed, KM2 is closed, and the motor M2 runs. Due to the pull-in of KM2, its normally open contact is self-locking. After its other contact is closed, the STP1 stop button is short-circuited. Therefore, if STP1 is pressed by mistake, KM1 will not lose power and be released, and motor M1 will not stop. Only by pressing STP2 first to stop motor M2, KM2 loses power and its normally open contact is released, and then pressing STP1 can stop M1.