Rotate incremental encoder to output pulse when rotating, and know its position by counting equipment. When encoder is stationary or power failure, it depends on the internal memory of counting equipment to remember the position. In this way, after power failure, the encoder can't move at all, and when the incoming call works, the encoder can't lose the pulse due to interference in the process of outputting the pulse. Otherwise, the memory zero of the counting equipment will shift, and the amount of this shift is unknown, only after the wrong production result appears. The solution is to increase the reference point, and every time the encoder passes through the reference point, the reference position is corrected into the memory position of the counting device. Before the reference point, the accuracy of the position cannot be guaranteed. For this reason, in industrial control, there are methods such as finding the reference point first, turning on the machine and changing it. This encoder is determined by the mechanical position of the encoder, and it is not affected by power failure or interference.