Like the fork sensors, frame sensors are optical sensors, where the transmitter and receiver are placed facing each other in a U-shaped aluminum housing or a closed crossbar housing. Unlike the regular fork sensor, the frame sensor has not one but several transmitters and receivers placed opposite of each other. This results in an infrared light curtain, which allows the most small objects to be detected fast (5 kHz) and with high accuracy. The frame sensors are available with fork opening sizes of 40 to 250 mm, the resolution is 0.5 to 4 mm. The frame sensors have a 3-pin M8 connector. The sensitivity as well as the built-in pulse extender can be adjusted via a potentiometer.