About The Aprilaire 8811 Protocol AdapterThe Aprilaire 8811 Protocol Adapter is designed to support up to 32 communicating thermostats. Each Aprilaire 8811 Protocol Adapter features color coded flying leads as well as two RJ1 six wire type jacks. The Aprilaire 8811 Protocol Adapter includes a 9V DC transformer, DB9 connector and cable. The Aprilaire 8811 Protocol Adapter is compatible with all Aprilaire compatible software systems that use RS232 port for serial port communications.