ActronAir 2020-035B Digital Residential Indoor PCB is installed in the indoor unit of ESP Plus Series 2 residential split ducted systems and controls EC fan motor speed control, zone output management, and wall controller communication. When this board fails, complete loss of indoor unit operation and zone control -- replacing it with the 100% Genuine ActronAir 2020-035B restores all factory system functions without reconfiguration. Isolate power at mains before replacement -- live work on electrical components is dangerous and must only be performed by a qualified technician.