Data Physics offers a world leading range of low frequency, pressure compensated, moving coil hydrosounders.The UW-350 is a smaller and lighter device that provides a versatile operating bandwidth of 20 Hz to 20 kHz with excellent beam patterns up to 1 kHz. The average sound pressure level across the operating band is 165 dB re 1 µPa at 1 m, and the maximum operating depth is 188 m. This operating depth can be extended for deployment on the hull of deep diving nuclear or conventional submarines. The UW-350 is employed by the navies of many countries.Data Physics can also supply a range of systems incorporating segmented/ free flooded ring transducers with resonant frequencies as low as 500 Hz and with a sound pressure level capability in excess of 200 dB re 1 µPa at 1 m.  Data Physics has produced and supplied rings as large as 1.5 m diameter with deployment framework, cables, winch and A-frame.Calibration systems are also available with transducers arranged in configurations for towing or for static deployment. The transducers are arranged to produce excellent beam patterns from 20 Hz to 80 kHz in both horizontal and vertical directions. Such systems provide an accurate method of calibrating and proving the performance of other active and passive sonars.