The IVM6000 accepts a wide input voltage on the two “~” terminals. Consult the latest data sheet for up to date ranges, but at the timeof this post it was between 5V and 48V AC or DC.
AC voltage is preferred for long distance runs because it will have lower losses, and will also avoid accidental corrosion of wires due to electrolysis. Note that the power input to the IVM first goes through a “diode bridge” and therefore the polarity of the power wire connections does not matter. There is additional surge, discharge and lighting protection at the IVM as well.
The IVM will show and log errors on the local display, but two additional wires are required if you want the IVM to actually signal a contact closure at a control panel.
So 4 wires is the minimum suggested configuration, for future expansion it is suggested to run an 8 wire cable.