Can more than one GP1871F GP1971F Combo unit be networked together or are they standalone If so how many can be networked

​GP1871F/GP1971F Combo units were primarily designed to be standalone combo units. Up to four GP1871F/1971F Combo units can be connected to a common NMEA2000 bus. However, a max of two GP1871F/GP1971F Combo units can be connected to a DRS4W radar sensor at the same time. Also, only one GP1871F/GP1971F Combo unit can display the ¼ screen virtual Navpilot 300 or 711C control window at a time and only the unit connected to the transducer will display a sounder image.