Gems^® Series Dual function Series DF models are designed to control two independent level functions: one single-level control operation and one differential-level operation. Optional Power Outage feature resets after nuisance outages. Optional Reset Button is used when the device has been deactivated due to low-water condition. Reset is activated only after water has returned to normal level. This control is ideal in applications on boilers, food service equipment, and chemical delivery systems.