Jay Electronique SJBT410A Light Curtain is a safety‑critical sensor array used to detect personnel or objects near moving machinery, typically operating on 24 VDC and outputting a 0–20 mA signal to an interlock controller. Common failure modes for this class of light curtains include broken optical fibers or lenses, power supply dropout, faulty transmitter/receiver electronics, and misalignment of the sensor array. First‑check diagnostics: verify 24 VDC input voltage and continuity on the power leads; inspect the transmitter and receiver housings for physical damage or dust buildup; confirm that the output signal (0–20 mA) is within spec using a multimeter or oscilloscope, and review any error codes displayed by the connected safety controller.[oss-gpt-20b]