*3.3. Online Detection*

Once the DTDA is trained, the common temporal feature representation can be obtained. The source domain label classifier *Gy*(·) can then be used well to recognize the fault in the data of the target domain. Therefore, in the online stage, the sequentially collected data batch is directly fed into *Gy*(·) to determine if a fault has occurred. This process does no need to re-train the DTDA, while the main computational cost is the linear calculation in *Gy*(·). As a result, the detection speed is very fast.
