F77 series ultrasonic sensors are designed to fit in tight spaces. These miniature sensors are suitable for dirty and dusty application environments and can handle color variations or transparent targets. Because they can detect objects within an area rather than being restricted to sensing only what is directly in front of them, the series can be used in applications in which the pin-point accuracy of a photoelectric beam is too focused to sense the target accurately. These sensors are immune to acoustic interference and have minimal deadband, which is important for sensors mounted on machinery with noisy pneumatic cylinders.