What D4BS15FS is and where it goes
The Omron D4BS15FS is a safety-door switch from the D4BS limit-switch line, built around a key actuator that engages only when the matching guard interlock is closed — the standard fit on hinged and sliding machine guards where a plain lever switch could be defeated. Contact arrangement is 1NO / 1NC, the conventional pair for a guard interlock where one pole feeds the safety circuit and the other carries the auxiliary to the contactor coil. It belongs to the Limit Switches category and is sized for panel-side mounting rather than DIN-rail distribution hardware. The package is 111.5 mm tall × 40 mm wide × 43 mm deep in an aluminium housing sealed to IP67, so the body tolerates the coolant splash, washdown, and outdoor exposure typical of machine-tool and conveyor guard locations. Four selectable head directions let the installer orient the key entry to match the guard swing or slide without re-machining the bracket.
Reading the 10 A contact rating for guard duty
The switching rating is 10 A at 250 VAC — the headline figure that decides whether the contacts can directly switch the safety contactor coil or need a relay interface. On a typical guard interlock loop feeding a safety relay or contactor coil drawing well under an amp, 10 A gives wide headroom against contact welding; the limit matters more on machines where the same switch also has to break a higher-current auxiliary load such as a guard-open indicator lamp circuit or a solenoid. Switching current and voltage here are stated in AC terms; inductive DC loads would derate the figure and are not implied by the AC rating on its own. Service life is rated at 500,000 electrical cycles and 1,000,000 mechanical cycles, meaning the mechanical wear on the key entry and head mechanism outlasts the contact wear by roughly 2:1. On a guard that cycles a few times per shift, electrical life is the binding constraint; on a high-cycle test-cell or assembly robot that opens and closes hundreds of times per day, mechanical life sets the maintenance interval. Either way, replacement is a planned event, not a failure mode, and a spare held against the BOM is the standard mitigation.