The head unit comes with the same dimensions for the display, 7-inch diagonal, 800H x 480V pixel resolution, but provides superior images, 16:9, brilliant color and crystal-clear. It’s also LED backlit, which makes it easily readable in harsh sunlight or during night time. It has a power output of 500 Watts (RMS) / 4,000 Watts (PTP).
In terms of sonar capabilities, the 859ci HD DI Combo, comes with Down Imaging and Dual Beam Plus Sonar. The DI sonar can operate at two frequencies, 455 kHz / 75°, or 800 kHz / 45° with a depth capability up to 350 ft. The Dual Beam Plus sonar can also operate at two frequencies, 200 kHz / 25° and 455 kHz / 16°, with a depth capability up to 650 ft. The standard transducer of this unit is a Transom XNT 9 DI T.
The navigational capabilities of this unit include precision GPS, chartplotting and trackplotting. It can store up to 2,750 waypoints, 45 routes and 50 tracks (20,000 points each). It has the CountourXD cartography package, and can be upgraded with a Lakemaster or Navionics Gold/HotMaps SD card. Does not support 360 Imaging or Navionics Platinum. However, it does support Radar2 and NMEA2000, but these are optional.