The smallest ultrasonic sensors are the zws Sensors in the miniature housings market. They contain a Teach-in button. It is contained in a cuboidal housing. This device is compatible with a variety of optical sensors. For critical applications it is the truest alternative. The switching frequency is up to 250 Hz for the fastest sampling. The most optimal conditions with SoundPipe attachnment for waveguide input of synchronization. The basics consist of switching output of either pnp or the npn variant. There are six detection ranges with a measurement range of 20mm up to 1 m available.