Slot and slot grid sensors work according to the familiar principle of thru-beam sensors and are often used for detecting objects of all kinds on vibrating and oscillating conveyors. The special U-shaped design means the transmitter and receiver can be accommodated in one housing, which achieves high resistance to vibrations. There is no time-intensive adjustment of the transmitter and receiver lenses and only one device to be wired. Slot sensors are especially suited to detecting small parts over short distances.