A shift register is a kind of signal transfer device integrating storage elements (memory devices). When an object is detected inline for sorting, ejecting, processing, etc., it is often impractical to use the signals for immediate control. In a coating line, for example, coating at the moment of detection may have an adverse effect such as splashing the paint on the sensor, which requires some distance between the position of detection and control.

Shift registers are convenient for use in these situations. The data signals generated at the moment of detection are stored and sent to the point of control in the order they are required.