When a production line needs to verify that a connector has been correctly mated before the next soldering step, the optical sensor with a stationary detection zone and dual‑polarity output becomes the gatekeeper for the entire assembly sequence. The sensor is mounted directly on the wiring harness fixture; as soon as the metal contacts align, the light path is interrupted, triggering a change in the NPN or PNP output that immediately stops the conveyor and alerts the PLC. This instant feedback prevents mis‑wired bundles from reaching downstream stations, eliminating costly rework and downtime. Because the device integrates its own signal conditioning, wiring technicians can link it to the control cabinet with a single cable, simplifying harness design and reducing the number of spare parts on hand. In modular automotive component factories, the same sensor is used to confirm that a door‑panel harness is fully seated before the door‑closing actuator is energized, ensuring safety interlocks are met without additional external relays. The result is a streamlined assembly flow where each step is validated in real time, keeping the line moving only when the wiring is truly ready.