Both the Partner ACS and Merlins are required to be grounded by at least a #12 AWG ground (Green or Gray or a predominance of Green or Gray, as per the NEC). Grounds should be attached to an approved ground, i.e. earth ground, building steel, cold water pipe (again, as per the NEC). In addition, you should have at a minimum, CO line protector(s) such as the towerMAX series, and AC surge protection. For some installers out there, a piece of jumper wire run to the screw of an electrical outlet does NOT constitute a proper ground.
IROB's should be used anytime a set is located off site and requires 2 for each telephone (1 at each end).
Partner phones work fine with the Merlin (016 ETR module), though I've never paid attention as to whether the backlight is always on.
franke