A Photo Interrupter is a transmission-type photo sensor, which typically consists of a light emitting elements and light receiving elements aligned facing each other in a single package, that works by detecting light blockage when a target object comes between both elements, acting as an optical switch. In behaviour science, ports are commonly used in experiments. Several different port systems and designs exist and ports can feature visual, auditory or olfactorial stimuli or provide rewards such as water or food for the correct behavior. It is important that the port design (shape, size, position of sensors etc) and the material (color, hardness, odor and/or surface smoothness) are adapted to the experimental goals and the used animals. Port entries and exits can, for example, be monitored via an infrared beam. Visual or auditory cues can be integrated in the port or adjacent to it. Together with the Medical University of Vienna we currently refine ports for experimentation on rat behaviour.