This article applies to the following CoolMaster products: CoolMaster CoolMasterPro CoolMasterNet * For Mitsubishi non-VRV equipment, DC voltage supply by CoolMaster might be required for proper operation. HVAC Communication TerminalsHVAC Indoor connection * Polarity is not required on the HVAC communication line. Measure DC voltage on HVAC comm. Line 1 If no 14-16V DC voltage, change the dip switches as shown below: Turn ON the power for CoolMasterNet and connect it to HVAC line. Connect to the communication terminals on the HVAC equipment and secure the cables in L1 line plug. Insert the plug into CoolMasterNet L1 socket