ActronAir 2020-087B Digital Residential Indoor PCB provides EC fan motor speed control, zone output management, and wall controller communication for ESP Plus Series 2 residential split ducted systems, forming the primary control interface between the wall controller, zone outputs, and refrigeration circuit. Board degradation typically presents as intermittent fault codes or erratic operation before complete failure -- complete loss of indoor unit operation and zone control confirms the board rather than a sensor or wiring fault. Isolate power at mains before replacement -- live work on electrical components is dangerous and must only be performed by a qualified technician.