2NC forced-guided contacts for safety interlock circuits
The D4BS4AFS carries a 2NC contact configuration — both contacts are normally closed and mechanically linked so that no NC contact can open unless the actuator releases, and no NC contact stays closed if the actuator is forced. That forced-guiding is what makes it a safety-door switch rather than a standard limit switch: in a guard circuit the PLC or safety relay sees a de-energized contact when the door is open and a confirmed closed path when it is shut — there is no single-contact ambiguity in the safety logic. Rated 10 A switching current at 250 V AC, the D4BS4AFS sits comfortably in the Class A or B contact rating band for industrial control circuits — it will carry and interrupt a motor starter coil, a pilot-light load, or a safety relay input without the contact welding that a resistive full-load rating would surface.
IP67 sealing for wet and dusty environments
IP67 means the switch body is sealed against dust ingress and survives temporary immersion — the 40 mm × 40 mm face and the barrel geometry keep the sealing at the door-entry point, not relying on an auxiliary gasket. For a machine guard on a food-conveyor line, a car wash, or an outdoor press enclosure, that is the rating that tells you the switch does not need a supplemental enclosure.
Mechanical versus electrical service life — which one governs your spares interval
The mechanical service life is 1,000,000 cycles; the electrical service life drops to 500,000 cycles at the rated load. For a guard door that cycles 50 times per shift, 500,000 cycles is roughly 27 years of electrical life — well past most machine lifetimes. But for a high-cycle indexing table or a packaging-line jam-clear door cycling 500 times per shift, the electrical endurance figure governs the replacement interval, not the mechanical. Source the spare before the electrical count runs out, not when the switch physically fails.