Who can explain the working principle of electric pressure cooker (which kind of electric timer) in detail?

The circuit structure of the pot is described as follows:

The pressure switch is connected in parallel with the timer (corresponding to the short circuit of the timer motor under normal circumstances) and then in series with the timer switch (this part is marked as A-B), and the contact switch of the thermal insulator is connected in parallel with the heat-insulating lamp with resistance (corresponding to the short circuit of the heat-insulating lamp under normal circumstances) (this part is marked as C-D) and then in parallel with (A-B), that is, the thermal insulator and the heat-insulating lamp are connected in parallel (timing motor, heat-insulating lamp). The heating lamp and the heating plate are connected in parallel (marked E-F). The combination of (A-B)//(C-D) is connected in series with (E-F) and temperature limiter. Plus the thermal fuse and finally connect the power plug. Under normal circumstances, use a multimeter to measure the power plug before electrifying, and whether the timer switch is turned on or not, you can measure the resistance of the heating plate. Turn on the power supply, and the heating lamp lights up (the power supply passes through the contact between the insulator and the heating plate). After turning the timing switch, a branch of the pressure switch is added to the power supply circuit, and the insulator is disconnected when the pressure reaches the set temperature. When the timer is started (connected in series with the heating plate), the heat preservation lamp lights up at the same time. If the plug is unplugged at this time, the resistance of the motor can be measured (18K). During walking, the heating lamp turns on and off until the end. If the timer does not work when the heating lamp is turned off, the resistance measured by unplugging the plug is infinite, that is, the circuit such as the motor is blocked. The problem is: if there is a problem with the motor alone, the insulated lamp should be on (the insulation device and the pressure contact are disconnected, and there is a voltage drop at both ends of the lamp), but it can't go; If the insulation switch does not trip, the insulation lamp will not light up and the timer will not go, but the heating plate is connected in series in the circuit at this time, and the heating lamp should light up. The pressure switch should be normal (the heating lamp goes out after the float rises and can be replaced repeatedly). The timer switch is broken, the motor does not go, and the heat preservation lamp and the heating lamp should be turned on alternately. Check that there is no problem with the internal threaded joint (marked immobile), and manually change the measured resistance values of the pressure switch and the insulation switch.