Supports conventional gas, oil, or electric applications (up to 2H/2C) when used with the W8635A Equipment Interface Module (EIM). It supports single-stage or multi-tage heat pump applications (up to 2H/1C) when used with the W8635B Equipment Interface Module (EIM).

• Use up to three thermostats with required W8635A,B EIM and optional W8703A Damper Interface Module to enable these features:
  — Seven-day programmable
  — Programmable fan
  — One-touch Daylight Savings Time key