Bistable circuit control motor forward and reverse circuit

The circuit is shown in Figure 3-72. This circuit uses a deformed bistable circuit to automatically control the forward and reverse operation of the motor and
has a shutdown delay process (time is adjustable) when the motor switches between forward and reverse rotations to protect the motor from impact. In the figure, sQi and
SQ2 are forward and reverse terminal limit switches respectively. The shutdown (delay) time
    can be changed by adjusting the values ​​of R], R2, C, and Cz and selecting voltage regulator tubes Vsl and vs? of different models and specifications.