F77 Series ultrasonic sensors from Pepperl+Fuchs Inc., Twinsburg, OH, are 31 by 11 by 23 mm and are an alternative to background-suppression photoelectric sensors. The sensors are available in diffuse (measuring range up to 400 mm), retroreflective (range up to 400 mm), and throughbeam (range up to 800 mm) versions and provide one pnp NO or NC switch-point output, use discrete PLC inputs, offer high or low-frequency options, have 2 Hz/mm max. resolution, and up to 50 Hz switching frequency. They are insensitive to object color, provide reliable clear object detection, and ignore target holes and ridges. They also have high immunity to acoustic interference and have minimal deadband.