Thyristor controlled motor timing forward and reverse circuit a

The circuit is shown in Figure 3-69. It is suitable for occasions where frequent timing control of forward and reverse operation of the motor is required.
    In the figure, the thyristors Vl, V2, V7, and vs are used for forward control, and V3, V4, V5, and V6 are used for reverse control;
the forward and reverse running times of the motor are respectively composed of single-junction transistors VTi and other delays. It is controlled by time circuit and
delay circuit composed of VTz, etc.; resistor R and capacitor C are used for thyristor protection.     By adjusting the potentiometers RPi and RPz, the forward and reverse running times of the motor can be changed respectively.