Hydrotrac Single Frequency Portable Hydrographic Echo Sounder The Hydrotrac portable echo sounder is an “all-in-one” recorder, digitizer and transceiver.  The unit is waterproof (with the lid closed) and easily transportable. Although simple to operate, it employs highly integrated digital and analog circuitry, proven display technology and power efficient thermal printing techniques. Two 16-bit processors share the real-time tasks of digitizing, printing, and interfacing, making the lightweight system an extremely capable instrument.