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The EM 120 multibeam echo sounder is designed to perform seabed mapping to full ocean depth with an unsurpassed resolution, coverage and accuracy. The system is cost effective, reliable, and easily operated on workstations with familiar operating systems. The EM 120 is a complete system. All necessary sensor interfaces, data displays for quality control and sensor calibration, seabed visualization, and data logging are a standard part of the system, as is integrated seabed acoustical imaging capability (sidescan). The operating frequency of the EM 120 multibeam echo sounder is 12 kHz. This frequency is standard for deep ocean echo sounding, and gives a good balance between reasonably small dimensions, narrow beams, and good range capability. The system has 191 beams with pointing angles automatically adjusted according to achievable coverage or operator defined limits. The beam spacing is normally equidistant, corresponding to 1 % of depth at 90 degrees angular coverage, 2 % at 120 degrees and 3 % at 140 degrees. Equiangle beam spacing is also available, as is an in-between spacing. Other features include a swath width up to 5.5 times the water depth, data collection in depths ranging from 20 to 11,000 meters, and real-time ray bending and attitude compensation. The EM 120 multibeam system was in production from 2000 to 2008 and was replaced with the EM 122.