||A digital echosounder designed for underwater acoustic assessment and monitoring of physical and biological features. The instrument may be used in either marine or freshwater environments, for mobile or autonomous fixed location surveys. The BioSonics DT-X echosounder consists of a surface unit with LINUX-based embedded processor, a digital transducer with cable, a Global Positioning System (GPS) receiver, and a notebook computer for communication, real-time display and data storage. The instrument can operate single-beam or split-beam transducers, allowing for the network of up to four separate transducers at four different frequencies. Operating frequencies include 38 kHz, 70 kHz, 120 kHz, 200 kHz, 420 kHz and 1000 kHz. Standard DT-X transducers may be deployed at a maximum of 100 m depth; the recommended maximum range depends on the transducer configuration: 995 m (single-beam), 497 m (dual-beam) or 248 m (split-beam).