Dual setpoint/deadband pneumatic room thermostats are designed for proportional control of pneumatic valves, damper actuators, and other final control devices in environmental control systems. These devices are for use when it is desirable to set up a temperature span within which the HVAC system uses no energy for heating or cooling between selected heating and cooling setpoints. The high capacity, two pipe, pilot-operated relay type design provides pneumatic feedback for accuracy and stability over the entire operating range.