Atwood provided faulty instructions- the so called 7.5 volt is not used- terminal 4 on the thermostat needs to be hooked to ground. If Atwood had just used standard terminology it would be easier- they show terminal 4 as relay common- a.k.a. rc and rw combined. Because DuoTherm switches the ground side of the relays, you need to provide a ground to rc and rw.
Given that they made that error, I'm not sure if the high fan will work correctly, because DuoTherm uses a relay for fan, then a relay to toggle between high and low. RVP uses a high relay and a low relay- IOW, both fan relays need to be energized for high fan for DuoTherm, single relays need to be energized for RVP. I assume that the note about the jumper deals with this issue...
The new Dometic digital system will ONLY work with the Dometic thermostat- it is a single comm wire setup, truly digital, not just a digital display on an analog setup, like all of the standard Hunter, et.al.
