The Aprilaire 8819 Distribution Panel is a switch controlled communication bus that can be wired to 8 Aprilaire Model 8800 thermostats. It cannot be used with model 8870 thermostats. You must use the 8818 distribution panel if you are using the older 8870 thermostat. This allows thermostat communication (transmit, receive, or both) to be turned on and off at one convenient location which simplifies installation and trouble-shooting. Each thermostat station on the distribution panel has an On/Off switch for power. This allows isolation of any one thermostat to simplify trouble-shooting. Order one 8819 Distribution Panel per every eight 8800 thermostats.