The Marine Data MD71THD is the dedicated Human Input Device (HID), control interface, and numeric heading display unit manufactured in the United Kingdom by Marine Data Systems Ltd. for Transmitting Heading Device (THD) systems. Operating alongside the MD97CSP Compass Sensor Processor within both Transmitting Magnetic Compass (MD71TMC) and Electromagnetic Compass (MD71EMC) architectures, the MD71THD manages sensor calibration, magnetic deviation and variation corrections, and heading data distribution.

Housed in a compact 96 x 96 mm DIN panel enclosure, the unit features a high-contrast 2.7-inch yellow OLED graphic display (128 x 64 pixels) that shows real-time digital heading alongside True or Magnetic source indicators and intuitive setup menus. Dual opto-isolated NMEA 0183 serial output channels transmit corrected heading sentences ($HDT, $HDG, $HDM) to bridge heading repeaters, ECDIS, RADAR, and autopilots.

Key Features:
• THD Control & Human Input Interface: Serves as the central operator control and calibration head for Marine Data TMC (MD71TMC) and EMC (MD71EMC) systems.
• Automatic & Manual Magnetic Corrections: Executes automatic sensor-to-compass / 390° swing calibration and allows manual entry of magnetic variation and deviation coefficients.
• High-Contrast 2.7″ OLED Display: Crisp 128 x 64 pixel yellow OLED screen presents clear numeric heading with True or Magnetic source indication and wide viewing angles.
• Dual NMEA 0183 Outputs & CAN Bus Link: Connects to the MD97CSP processor via a 9-way D-type CAN Bus link and provides 2 independent NMEA 0183 outputs ($HDT, $HDG, $HDM) via a 15-way D-type connector.
• Compact 96×96 mm DIN Footprint: Flush-mounts directly into bridge consoles with optional trunnion bracket mounting (MD71TB) and dual redundant 24V DC power inputs.