SmartZone-4X Control - 4 zone controller KIT w/Temp sensor - Universal Replacement for honeywell zoning panel truezone hz432 & more 4 ZONES up to 20 ZONES Universally Compatible - Works with any system (Gas, Elect, Heat Pump) Use any thermostats - nest, ecobee, honeywell, etc. EASY to install, Simple to use Built-In Fresh Air control, Economizer and other exclusive features Economy Mode allows setback of all zones with the flip of a switch. When in eco mode, the system will only energize if zone 1 makes a call. This feature is great for vacations or if some of the zones are rarely used. Fresh air control allows control of an outside air damper and the system fan on a schedule to bring in fresh air in a prescribed amount. If fresh air control is required, Smartzone-4x has it covered with no additional controls required. Save $ Smartlink: expand to 20 zones by simply connecting multiple 4X boards together with the smartlink bus. Easiest &amp; most cost effective system for more than 5 zones! Smart staging &amp; limit protection  by using a proprietary time and temperature algorithm perfected over decades of programming, smartzone stages up and down in the most effective and efficient manner possible. 2nd stage lockout  by setting this dip switch, smartzone will only allow 2nd stage if more than one zone is calling Stage from zone 1 thermostat  allows for a multi-stage thermostat to be connected to zone 1 and control zoning instead of smartzone (not recommended in typical circumstances) Best technical support and documents (full color install guide included with SmartZone &amp; best online documentation too)