Detects target capable of blocking light. Where the target passes between an emitting unit and a receiving unit, blocking the beam and causing the receiver to change states. These are separate, independently covered units.

Sensing Range: 0-50 m

Advantage: Best for long range or to look through a translucent object, tolerant of dirt.
Disadvantage: Requires both an emitter and a receiver.

Applications: Height verification, loop control, fill level.