  KM3NeT is a future multi-cubic-kilometre water Cherenkov neutrino telescope
currently entering a first construction phase. It will be located in the
Mediterranean Sea and comprise about 600 vertical structures called detection
units. Each of these detection units has a length of several hundred metres and
is anchored to the sea bed on one side and held taut by a buoy on the other
side. The detection units are thus subject to permanent movement due to sea
currents. Modules holding photosensors and additional equipment are equally
distributed along the detection units. The relative positions of the
photosensors has to be known with an uncertainty below $20\,$cm in order to
achieve the necessary precision for neutrino astronomy. These positions can be
determined with an acoustic positioning system: dedicated acoustic emitters
located at known positions and acoustic receivers along each detection unit.
This article describes the approach to combine an acoustic receiver with the
photosensors inside one detection module using a common power supply and data
readout. The advantage of this approach lies in a reduction of underwater
connectors and module configurations as well as in the compactification of the
detection units integrating the auxiliary devices necessary for their
successful operation.
