I think its much simpler, merely a pulse train.
Its the same for the "Ultrasonic" connection.
I put in an Airmar Ultrasonic speed transducer and connected it to the "Ultrasonic" connectors on the Hydra 2000. In the setup menu there's a calibration page where you can change the no. of pulses (frequency) per knot to calibrate the sensor.
If this new one is NMEA 0183 or 2000 it won;t work with the B&G Hydra 2000. But it will work with other brands that have NMEA0183 and/or 2000 interface capability.