Slot phototransistor — 0.047 mm gap, through-hole
The ROHM RPI-125 is a slot-type phototransistor with a 0.047 mm sensing distance, designed for through-hole mounting in a bulk package. It operates as an unamplified phototransistor output, meaning the collector-emitter current switches directly in response to the infrared beam interruption across the slot.
Key ratings and what they mean for the BOM
The 10 ms response time means the sensor settles within one mains cycle at 50/60 Hz — adequate for object-present detection on a conveyor or flag sensing in a mechanical interlock, but too slow for high-speed counting above 100 events per second. Rated for -25°C to 85°C operating temperature — this covers indoor industrial enclosures and outdoor cabinets in temperate climates, but not engine-bay or freezer applications below -25°C.