The Marine Data MD77HR is a compact, high-precision dial-type NMEA compass heading repeater display manufactured in the United Kingdom by Marine Data Systems. Designed for flush panel, bulkhead, or trunnion mounting inside vessel wheelhouses, chart rooms, and steering consoles, the MD77HR provides clear, real-time heading indications driven by shipboard gyrocompasses, satellite compasses, or magnetic heading sensors.

The unit features a high-contrast 150mm (approx. 6-inch) dual-scale dial card layout ( outer 360° scale with an inner high-magnification expanded scale) offering 0.1° heading resolution. Built into a compact aluminum alloy enclosure, the MD77HR automatically detects and decodes digital NMEA 0183 heading sentences ($HDT, $HDG, $HDM, $THS). It features adjustable red LED dial illumination for night-watch operations on the bridge without affecting night vision.

Key Features:
• 150mm High-Visibility Dial Display: Clear dual-concentric dial layout providing accurate visual heading indication with 0.1° digital resolution.
• Compact Panel & Bulkhead Mounting: Space-saving DIN/console footprint suitable for wheelhouse consoles, overhead panels, and steering stations.
• Universal NMEA 0183 Compatibility: Decodes serial NMEA 0183 data ($HDT, $HDG, $HDM, $THS) with automatic baud rate selection.
• Variable Red Night Illumination: Dimmable red LED backlight controlled locally via front rotary knob or remotely via NMEA serial commands.
• Marine Class Rugged Build: Corrosion-resistant aluminum alloy chassis engineered to satisfy IEC 60945 environmental and EMC standards for bridge equipment.