Airmar 'Smart' transducers contain active circuitry that converts the sensor data into a standard NMEA format. NMEA 0183 versions output standard NMEA 0183 sentences for connection to a display or multiplexer. These transducers must be connected to a 12v power supply. NMEA 2000 versions output standard NMEA 2000 data formats and have an NMEA 2000 drop cable attached, ready to plug into a T-connector on a network backbone. These transducers are powered by the network.
Smart depth transducers use the 235kHz frequency so as not to interfere with fishfinder transducers.
Note that there are no NMEA fishfinder transducers. Fishfinder transducers produce a large volume of analog data that cannot be converted to NMEA format.