Development of an acoustic transceiver for the KM3NeT positioning system
  In this paper we describe an acoustic transceiver developed for the KM3NeT positioning system. The acoustic transceiver is composed of a commercial free flooded transducer, which works mainly in the 20-40 kHz frequency range and withstands high pressures (up to 500 bars). A sound emission board was developed that is adapted to the characteristics of the transducer and meets all requirements: low power consumption, high intensity of emission, low intrinsic noise, arbitrary signals for emission and the capacity of acquiring the receiving signals with very good timing precision. The results of the different tests made with the transceiver in the laboratory and shallow sea water are described, as well as, the activities for its integration in the Instrumentation Line of the ANTARES neutrino telescope and in a NEMO tower for the in situ tests. 
G. Larosa, M. Ardid, C.D. Llorens, M. Bou-Cabo, J.A. Mart\'inez-Mora,   S. Adri\'an-Mart\'inez
physics.ins-det astro-ph.IM