The Model 200 lead/lag controller from Quest features factory-configured set points based on customer requirements, while the Model 201 allows for configuration and set point changes through password-protected menus. Both models provide precise control over two HVAC systems and offer a wide temperature control window to further optimize for energy savings. The Model 200 and 201 support HVAC units with built-in economizers along with units that have two stages of mechanical cooling. The controller is compact and easy to install as a replacement for a standard thermostat. Power to the controller is redundantly derived from both HVAC units so the system continues to operate if one of the HVAC units loses power. In addition, the Model 200/201 has separate normally closed contacts for high temperature and low temperature alarming.