OVERVIEW. The MD36/6 is a solid-state (S-Type) Step to NMEA Interface, designed as a converter of DC Step (S Type) transmission of a ship's heading from legacy equipment, to a modern NMEA 0183 compliant Digital Transmission format. There is an alignment facility on the unit to align the digital output of the MD36/6 to the incoming heading signal. NMEA 0183 wiring, why it bugs me. by Ben Ellison · May 23, 2006. OK, I admit that at least half of the hideous mess above is the fault of yours truly, being sloppy with a temporary install, in this case interfacing a DSC VHF, a GPS, and an AIS receiver all to a Garmin 3210 (possible because it has two 0183 ports, plus a special Garmin GPS port).