The Pearl topology refers to various modes of the controllers. Controllers can be set to these modes:

Gateway:  The controller that is connected to the weather station. It will broadcast the weather station data to all the other controllers through COM3. It is the Modbus master on COM3, thus the Addr field is not applicable.

Zone:  The controllers that are receiving the weather station data from the Gateway unit on COM3. These controllers are Modbus slaves, thus it needs to have its Addr(ess) field uniquely set. Keep in mind that, in order for the Zone controllers to receive their weather station data, the weather station data sensors (e.g. Outside temperature and humidity) need to be mapped to Remote. ** Refer to the Zone Settings screen for more explanations.